The United States probably played a role in the deaths resulting from a March 17 air strike in Iraq, a top US commander has said.
But Lieutenant General Stephen Townsend, the commander leading the fight against Islamic State militants, said it appears enemy fighters may have gathered the civilians into the building for use as human shields.
Witnesses say the strike may have killed at least 100 people.
Lt Gen Townsend said on Tuesday there is a "fair chance" the US launched the strike.
He said US personnel have visited the site to conduct tests and gather information. But he said the munitions used by the US should not have been able to bring down the entire building, raising questions about US involvement.
US air strikes are targeting IS fighters to help Iraqi forces retake Mosul.