During the Cuban intervention in Angola, United Nations toxicologists certified that residue from both VX and sarin nerve agents had been discovered in plants, water, and soil where Cuban units were conducting operations against National Union for the Total Independence of Angola (UNITA) insurgents. In 1985, UNITA made the first of several claims that their forces were the target of chemical weapons, specifically organophosphates. The following year guerrillas reported being bombarded with an unidentified greenish-yellow agent on three separate occasions. Depending on the length and intensity of exposure, victims suffered blindness or death. The toxin was also observed to have killed plant life. Shortly afterwards, UNITA also sighted strikes carried out with a brown agent which it claimed resembled mustard gas. As early as 1984 a research team dispatched by the University of Ghent had examined patients in UNITA field hospitals showing signs of exposure to nerve agents, although it found no evidence of mustard gas.