Paul Conroy, a US truck driver, awakens buried alive, bound and gagged, with only a Zippo and a BlackBerry. Although he initially has no idea as to how he got there, he soon starts to piece together what has happened to him. Gradually, Paul remembers that he and several other convoys were ambushed by insurgents, then all the other truck drivers were killed shortly before he blacked out. After finding the cellphone, Paul attempts to contact his wife and his employers (who gave him a safety number if anything like this should occur) but is able only to leave a message for both of them. Paul is able to contact the FBI, but they cut off before he can explain the situation. However, he is able to determine from the questions the FBI official asks him that he has been kidnapped. The kidnapper contacts him and demands a ransom of $5 million to release him alive, but this is then lowered to $1 million.Paul eventually gets into contact with the State Department, who pass him onto a group set up in 2004 specifically made to find people who have been kidnapped. While the man, Dan Brenner, who is trying to find Paul tells him that they are doing their best, Paul is not convinced and asks the man to name a person who they had saved before. He claims they saved a man known as Mark White three weeks ago. After a long time of his trying to get help, the kidnapper forces him to make a ransom video, which he refuses to do. The kidnapper threatens to kill his kidnapped co-worker, and Paul reluctantly agrees to do the video. Shortly afterwards, there is a violent shaking in the coffin, and sand starts to leak into it. He then receives a video from the kidnapper of the female employee he knew being shot dead, causing him to feel incredibly guilty and to vomit. The stress becomes too great and Paul momentarily considers slitting his own throat with the knife, but he stops after thinking about his family.Later on, he receives a phone call from his employers, who inform him that he was fired from his job that morning due to fraternizing with the same female employee (though Paul says the relationship was strictly professional) and so if he dies, his family will not get any insurance money. The government group calls Paul and explains that some F-16 fighter planes just bombed the area the coffin is in even though they knew he was in the area (they were able to roughly pin down his location, but not exactly). The sand starts to leak in at a considerably faster rate and Paul begins to lose all hope and does a last will and testament in video form, giving his son all of his clothes and his wife all of his personal savings ($700). As time goes on (with nobody planning to pay the ransom), the kidnapper calls with demands for blood instead of money and tells Paul to cut his finger off and send a recording of it. If he doesn't do this, the kidnapper will harm his family (as he reveals the details of where they live). If Paul does make the video, his family will not be harmed, and he will tell the US government where Paul is. With this, Paul complies, cutting his finger off and sending the video.Within a few minutes, the government official phones Paul saying they now know where he is, explaining that they were given details of where to find a man who was buried alive by an insurgent. Paul receives a phone call from his wife and tells her he is going to be okay, and they express their love for each other. A few minutes later, he gets a call from the rescue group saying that they are close and have found his location. They arrive at the apparent burial site and are about to dig up the coffin. Through the phone, digging is heard, but Paul cannot hear digging around him. Sand begins to fill the coffin to dangerous levels, giving Paul seconds left. However, when the group digs up the coffin, it turns out the insurgent led them to Mark White, the man Brenner earlier in the film claimed had been rescued. Paul hears his final words, that of Dan saying over the phone, "I'm sorry Paul. I'm so sorry."
Output: Question: What caused the explosions that damaged the coffin?, Answer: <No Answer>