The helicopter crash which claimed the life of Andhra Pradesh Chief Minister Y S R Reddy was caused by pilots' error who lost the chopper's control and were engrossed for vital six minutes trying to locate a flight manual, the probe report said today.

The report, submitted to the government by the four- member inquiry committee, said the "probable" cause of the accident was that it "occurred due to loss of control resulting in uncontrolled descent in the terrain at a very high rate of descent due to entry into severe down draught".

The crew flew the helicopter under the instrument flying condition even though their flight plan was cleared for Visual Flight Rules (VFR), it said.

The crew noticed a snag and "was engrossed for vital six minutes before the impact in searching for the relevant checklist from the Flight Manual".

"This distracted their attention from the prevailing poor visibility weather conditions thus leading into the loss of situational awareness," the report, prepared by the Committee headed by Pawan Hans Helicopters Limited chief SK Tyagi, said.