KABUL, Afghanistan, AP – The U.S.-led coalition raised the possibility Tuesday that a U.S. and a Canadian soldier killed in southern Afghanistan were victims of friendly fire.

The coalition said it would investigate the Taliban attack Saturday on a coalition base in Helmand province, “including whether any of the casualties may have resulted from friendly fire.”

Besides the two deaths, five soldiers were wounded in the attack: an American, three Canadians and an Afghan.

U.S. forces have suffered seven friendly fire casualties during their mission in Afghanistan, according to U.S. officials last month. A total of 222 U.S. troops have died in combat in and around Afghanistan over the same four-year period.

Canadian military officials would not say whether their forces have suffered friendly fire casualties in Afghanistan.

The best-known case of U.S. friendly fire in Afghanistan is that of Cpl. Pat Tillman, who was shot in 2004 near the Pakistan border. The Army initially said he had been killed by enemy fire, but later said he died by gunfire from his fellow Army Rangers.

The Defense Department last month announced an investigation into allegations of an Army cover-up in the death of Tillman, who turned down a lucrative NFL football contract to join the Army.