Hundreds of civilians have reportedly been killed in the March 17 US air strikes on suspected Daesh targets in the besieged Iraqi city.
The top American military commander in Iraq said on Tuesday that the US-led coalition probably had a role in the deadly blasts in Mosul that killed more than 200 civilians this month.
But he said investigation was still underway and Daesh may also be to blame.
The blast hit Al Jadida district on March 17 after US jets carried out air strikes targeting Daesh fighters.
"My initial assessment is that we probably had a role in these casualties. Now, here's what I don't know. What I don't know is were they (the civilians) gathered there by the enemy? We still have some assessments to do," Lieutenant General Steve Townsend told a Pentagon news briefing, speaking from Iraq.
"I would say this, that it sure looks like they were."
On Monday, US Army Chief of Staff General Mark Milley said that investigators have been sent to Mosul to determine whether it was a coalition strike or Daesh-rigged explosives that caused the explosion.
"It is very possible that Daesh blew up that building to blame it on the coalition in order to cause a delay in the offensive on Mosul and cause a delay in the use of coalition air strikes," Milley said.
"It is possible that a coalition air strike did it. We don't know yet. There are investigators on the ground."
The operation by US-backed forces to drive Daesh out of Mosul is in its sixth month.
Mosul's entire eastern side and about half of its western side is now under the Iraqi government's control.