The U.S. military acknowledged for the first time Saturday that it launched an airstrike against the Islamic State last week in the densely packed Iraqi city of Mosul where residents say more than 100 people were killed.

“An initial review of strike data … indicates that, at the request of the Iraqi security forces, the Coalition struck ISIS fighters and equipment, March 17, in west Mosul at the location corresponding to allegations of civilian casualties,” the task force leading the coalition said in a statement.

Previously, the U.S.-led coalition had said that officials were unsure whether the United States had conducted air attacks targeting the affected site in Mosul al-Jadida, where local officials say they have so far pulled at least 60 bodies from one destroyed building.

The U.S. military is conducting an initial investigation into the incident.

If confirmed, the incident would mark the greatest loss of civilian life since the United States began strikes on Islamic State targets in Iraq and Syria in 2014. The allegations add to questions about the conduct of the campaign to recapture Mosul, where reports of civilian deaths are rising as government-aligned forces advance through a fiercely contested urban area.

Airwars, a U.K.-based monitoring organization, has raised the alarm about what it says is a surge in recent weeks of reported deaths caused by U.S.-led airstrikes. The conduct of the air campaign is under especially close scrutiny in the early days of the Trump administration, which has promised to wage a more aggressive campaign against the Islamic State.

President Trump has already asked military leaders to consider whether requirements on U.S. military operations against the group should be loosened.

The U.S.-led coalition said its goal was “zero civilian casualties.”

“But the coalition will not abandon our commitment to our Iraqi partners because of ISIS’s inhuman tactics terrorizing civilians, using human shields, and fighting from protected sites such as schools, hospitals, religious sites and civilian neighborhoods,” the statement said.

An Iraqi military commander suggested the large death toll in the March 17 incident may have been partially caused by the fact that a missile struck a car bomb, unleashing a giant explosion. Rescue workers and residents described a hellish scene, where scores of civilians were killed in nearby buildings.

Islamic State fighters, seeking to defend areas of Mosul that remain under their control, have forced residents to remain in areas where fighting is taking place, even moving them into neighborhoods that are the scenes of fierce battles. The militants have also launched attacks from rooftops of residents’ homes.