For more than half a century, the circumstances of the tragic death of Dag Hammarskjöld have been shrouded in mystery. 
 
 That the former UN secretary-general died in a plane crash while on his way to negotiate a ceasefire in the breakaway African republic of Katanga, is well documented. But the cause of the crash remains to be established. 
 
 That proof may become available if the US National Security Agency (NSA) complies with a new request from the UN and hands over crucial intelligence intercepts that could confirm what brought down the Albertina DC6 in a forest near Ndola in northern Rhodesia (now Zambia) in September 1961. All but one on board died in the crash. A 16th passenger, Sergeant Harold Julien, the acting chief security officer, died as a result of injuries a few days later, having told medical staff he had seen “sparks in the sky” shortly before the crash. 
 
 Three separate inquiries have been unable to come to a definitive conclusion about what happened on the fateful night. Since then, conspiracy theorists have gone into overdrive, possibly with good cause. The day after the crash, former US president Harry Truman told reporters Hammarskjöld “was on the point of getting something done when they killed him. Notice that I said ‘when they killed him’.” Truman refused to elaborate but this served only to fuel the rumour mill. 
 
 Many countries had an interest in thwarting Hammarskjöld’s attempts to reunite Congo and stop Katanga seceding. Congo, which was receiving Soviet aid, had the world’s richest uranium resources. Mining firms feared their concessions would be jeopardised if Katanga’s bid for independence was not recognised. The KGB, the CIA and MI6 were all active in the country as they sought to secure their countries’ interests. 
 
 A report from a panel of distinguished international jurists, commissioned by the Hammarskjöld Inquiry Trust, chaired by Lord Lea of Crondall and submitted to the UN last year, heard suggestions “that a group representing a number of European political and business interests ... wanted the secretary-general’s plane diverted from Ndola ... in order to persuade him of the case for Katanga’s continued independence”. 
 
 Quite how forcefully such interests may have made their case could explain the cause of the crash. Several people who attended the crash scene claimed the Albertina was riddled with bullets. A delay of more than nine hours in locating the plane has triggered speculation that the crash site was interfered with. Several witnesses said they saw between six and eight white men, armed and in combat fatigues, at the crash site. 
 
 Then there are lurid claims that some on board, including Hammarskjöld himself, had bullet wounds, suggesting he had survived the crash but had been killed on the spot. His body was found propped up on a termite mound a short distance from the plane, surrounded by playing cards. Reputedly an ace of spades was found on his collar. 
 
 In the aftermath, loose-lipped mercenaries claimed that they had played a part in the operation. In 1998 the South African truth and reconciliation commission published intelligence documents suggesting that a bomb had been placed on board. A separate CIA report implicated the KGB. 
 
 Given so many competing claims, some doubt whether the truth will ever surface. But tomorrow the UN will signal that the investigation into what happened should be reopened, when it is expected to pass a motion asking member states to provide it with any information they have on the affair. 
 
 The resolution is more than a symbolic gesture. It is believed that the US National Security Agency is in possession of radio intercepts, captured by its listening station in Cyprus, that will prove or disprove whether a second plane was in the air near Ndola shortly before the crash. If so, this would help corroborate claims made by a former Belgian pilot called Beukels that he accidentally shot down the Albertina in an attempt to divert it from Ndola to another airport. 
 
 Facebook Twitter Pinterest Dag Hammarskjold died in a plane crash in 1961. 
 
 Beukels said he shone a bright light down from his Fouga jet onto the cabin of the DC6 while his radio operator called on the plane to divert. After failing to receive a reply, Beukels fired several warning shots which clipped the Albertina’s wing, causing it to crash. 
 
 The report commissioned by Lea suggested that the NSA’s intercepts could be the “golden thread” that finally unravels the mystery. It stated that “it is highly likely that the entirety of the local and regional Ndola radio traffic on the night of 17-18 September 1961 was tracked and recorded by the NSA, and possibly also by the CIA”. In his letter introducing the report to the UN, Lea observed that “there is persuasive evidence that the Hammarskjöld aircraft was subject to some form of attack as it circled Ndola”. 
 
 So far requests to the NSA to produce relevant intercepts have been denied. But a direct appeal from the UN may cause the agency to think again. As the report notes: “It is thus possible that the last half-century, far from obscuring the facts, may have brought us somewhat closer to the truth about an event of global significance which deserves the attention both of history and of justice.” ||||| The United Nations’ general assembly is set to approve a fresh inquiry into the death of the organisation’s secretary-general, Dag Hammarskjöld, in a 1961 air crash. 
 
 Sweden will present a resolution to the assembly on Monday calling for the creation of an independent panel of experts to look at one of the great political mysteries of the 60s: why a plane carrying one of its most famous diplomats came down over what is now Zambia, but was then the British colony of Northern Rhodesia. 
 
 The resolution cites the emergence of new evidence and calls for the UN panel to examine it “and to assess its probative value”. It also appeals to governments to release documents about the Hammarskjöld crash that have remained secret until now. The resolution has 20 co-sponsors from around the world and is expected to win overwhelming support. 
 
 “I would expect a consensus decision to be taken, so it would be passed by acclamation,” Annika Söder, the state secretary in the Swedish foreign ministry, said. “I can’t see anyone being against steps for getting clarification.” 
 
 Söder said there could a delay of in earmarking the necessary funds for a panel of experts – initially about $300,000 (£240,000) – but that should only take a further week. Once established, the panel could request crucial documents about the crash from the US National Security Agency and the CIA, as well as still-classified records held by the UK and other western European states. 
 
 The plane in which Hammarskjöld and his staff were travelling crashed near the town of Ndola, while the UN secretary-general was trying to broker a peace deal between the Congolese government in Kinshasa and separatists in the mineral-rich southern province of Katanga backed by mining corporations and mercenaries. 
 
 A 1962 report by the British colonial authorities in Rhodesia blamed the crash on pilot error but offered no proof. A UN inquiry returned an open verdict. Since then new evidence has come to light, including the testimony of local people that was downplayed or ignored in the original report. 
 
 The new material was published in a 2011 book, Who Killed Hammarskjöld? The UN, the Cold War and White Supremacy in Africa, by a British academic, Susan Williams, who argued that Hammarskjöld was shot down by mercenaries fighting for Katanga. The Guardian also published a report the same year, based in part on the research of a Swedish diplomat, Göran Björkdahl, which cast doubt the official version of events, and pointed to the possibility a second plane had been close to the UN aircraft. 
 
 Williams welcomed Monday’s vote, saying: “There is no better way to reassess the history of colonisation and the cold war than through the leadership of the United Nations.” 
 
 Last year, a commission of international legal experts, including Richard Goldstone, the former chief prosecutor at The Hague’s war crimes tribunal, called for the case to be reopened and appealed to the US and other governments to declassify secret documents on the crash. In particular, it presented a formal request for the declassification of NSA and CIA intercepts from the night of the crash on 17-18 September 1961, but without success. 
 
 “We know they must have listened to the radio traffic that night and transcribed it,” Hans Corell, a Swedish judge and former diplomat who was a member of the Hammarskjold commission, told the Guardian. “The NSA had station in Cyprus, where they were listening to high-frequency transmission. 
 
 “We also know the CIA had two Dakota planes on the tarmac in Ndola that night with their engines running. Why would a plane have its engine running in the middle of the night? To run the generators, for the interception equipment.” 
 
 The commission was told there were classified US intelligence documents relevant to its inquiry, but they were not released. Its members hope that a panel requesting the information in the name of the UN will have better luck. 
 
 In March 2014, the UN secretary general, Ban ki-Moon, issued a statement saying: “Additional new evidence may exist which, for national security reasons, was and remains classified by several governments more than 50 years after the fact. 
 
 “I trust that the general assembly may wish to encourage member states, in the light of the passage of time, to seek to declassify any relevant records in their possession in accordance with their respective national legislation.” 
 
 Söder said: “Earlier investigations were not at all certain in their judgment. We hope for full clarity. Dag Hammarskjöld was an important statesman, one of several political personalities who have died in unclear circumstances. 
 
 “But there are also the families of the other people on the plane. The family of the Swedish pilot for example. The official inquiry blamed pilot error. But what if that was wrong? It would be good if it was either confirmed or proven wrong.”
– For more than 50 years, the death of Swedish diplomat Dag Hammarskjold has remained one of the era's biggest mysteries. The UN secretary-general's plane plummeted out of the skies in September 1961 in Northern Rhodesia (now Zambia) as he flew to orchestrate a ceasefire between Congo's government and Katanga province separatists; a 1962 crash report pointed the finger at pilot error, the Guardian reports. But with new evidence reportedly on the table, including testimony from locals that had been previously swept under the rug, Sweden will today ask the UN to form an independent panel to assess the evidence. The panel would be able to appeal for NSA and CIA files on the crash, as well as classified documents from the UK and other countries. Rumors have run rampant since the crash, including one that claims a second plane had been near Hammarskjold's Albertina DC-6, the Observer notes. The acting security chief on Hammarskjold's plane—who died of his injuries a few days after the crash—reportedly told medical staff he had seen "sparks in the sky," while a Belgian pilot claimed he sent the Albertina crashing down by mistake after he fired warning shots at the plane's wing. Other witnesses insisted they saw the Albertina sprinkled with bullets and men in combat uniforms at the crash site, and there were whispers that Hammarskjold had been shot and was found on a termite mound with an ace of spades playing card on his collar. It didn't help stave off conspiracy theories when former President Harry Truman said the day after the crash that Hammarskjold "was on the point of getting something done when they killed him."