Moscow ? A military helicopter crash that killed 114 people in Chechnya was most likely caused by a rebel attack from the ground, Russia’s chief prosecutor said Tuesday, and a news agency reported that a missile launcher had been found nearby.

Monday’s crash outside the Russian military headquarters at Khankala has been described by media as the country’s worst military air disaster.

“We are investigating several theories of the cause of this incident, but we consider the theory of fire from the ground to be the main one,” prosecutor General Vladimir Ustinov said, according to the Interfax news agency.

Citing an anonymous source at the Khankala headquarters, Interfax reported that investigators found a Strela anti-aircraft missile launcher that had been used to shoot down the Mi-26 helicopter. Chechen rebels on Monday claimed that they had shot the helicopter down.

“There was a flash to the right, near the engine, then a bang, and then a black kerosene cloud veiled everything,” Sergei Shishayev, a soldier who survived the crash, told RTR television from his hospital bed. “I felt like I was dreaming, then I lost consciousness.”

Officials at first gave widely differing accounts of how many people had been on board the helicopter and how many had been killed. On Tuesday evening, Defense Minister Sergei Ivanov said 114 out of 147 people on board were killed.

All five of the crew survived the crash.

President Vladimir Putin declared Thursday a day of mourning for those killed in the crash.