U.S. troops tried to burn about 500 copies of the Koran as part of a badly bungled security sweep at an Afghan prison in February, despite repeated warnings from Afghan soldiers that they were making a colossal mistake, according to a U.S. military investigative report released Monday.

The number of copies of the Muslim holy book that were taken to the incinerator at Bagram air base was far greater than U.S. military officials earlier acknowledged in their accounts of an act of desecration that triggered riots across Afghanistan. The incident is also thought to have played at least a partial role in an ensuing increase in attacks against NATO troops by Afghan soldiers and police.