The commander of the international coalition in Afghanistan has apologized and promised an investigation into reports that NATO personnel mishandled Islamic religious texts.

U.S. General John Allen said in a statement Tuesday that he ordered a “thorough investigation” after learning that coalition forces at Bagram Airbase may have “improperly disposed” of a large number of Islamic religious texts, including Qurans.

Allen insists the incident was not intentional. He apologized for any offense caused to the people or government of Afghanistan, saying NATO is taking steps to make sure that this “does not ever happen again.” He said the texts have been given to religious authorities to be “properly handled.”

Following the reports, a group of at least 1,000 protesters gathered outside Bagram Airbase to denounce the alleged destruction of the Quran.

Afghan protests against the destruction of the Muslim holy book have turned deadly in recent years.

In April 2011, about 20 people were killed during several days of protests across Afghanistan after little-known U.S. pastor Terry Jones burned a Quran at his small Florida church.