The United States has admitted that at least 105 Iraqi civilians were killed in an air strike it carried out in Mosul in March.
US Central Command (CentCom) said it had targeted two snipers from so-called Islamic State (IS) with what it called a "precision-guided munition".
However, the strike detonated explosives that militants had placed in the building, CentCom said.
Civilians sheltering in the lower floors were killed when it collapsed.
In another incident, 35 civilians were killed on Thursday in US-led coalition air strikes in an eastern Syrian town, monitors said.
The strikes targeted the IS-held town of Mayadeen in the province of Deir Ezzor, according to the Syrian Observatory for Human Rights. Families of IS fighters, including children, were among those killed, it added.
CentCom said the death toll in the March attack in Iraq included four civilians in another nearby structure.
Eyewitnesses claimed another 36 non-combatants were also in the building, but US authorities said it had "insufficient evidence to determine their status".
CentCom previously said the planes had acted at the request of Iraqi security forces, as coalition forces attempted to wrest control of the city from IS.
The civilians had gathered in the lower floors of the building after being expelled from their homes by IS fighters, a declassified summary of the report said.
Those organising the strike "could not have predicted the presence of civilians in the structure prior to the engagement," it added.
US officials said the type of bomb was chosen "to minimise collateral damage," but the explosives hidden by IS were at least four times more powerful than the weapon itself.