The Pentagon admitted that two civilians were in fact killed in U.S.-led strikes against the Islamic State group (ISIS), according to a report from The Daily Beast.

Two defense officials told The Daily Beast that an internal U.S. Central Command (CENTCOM) investigation revealed the deaths, which are expected to be detailed in an upcoming report.

The admission marks the first time that the U.S. military has acknowledged killing a civilian since the campaign against ISIS began nine months ago. Pentagon officials previously told The Daily Beast that there was no definitive way to determine whether a civilian had been killed.

Specific details of the deaths were not provided to the Beast, but CENTCOM officials previously said they were investigating allegations of civilian deaths in four cases, from Aug. 8, 2014 to mid-March of 2015, according to The Daily Beast.

A U.S.-led April 30 bombing in the Syrian town of Bir Mahli resulted in the death of 52 civilians, according to the Britain-based Syrian Observatory for Human Rights. The group called the killings a "massacre" committed under the "pretext" of targeting Islamic State militants.

The U.S. military's account is much different, with officials saying shortly after the attack that it killed 50 ISIS fighters in a largely abandoned village.

"We currently have no indication that any civilians were killed in these strikes," CENTCOM spokesman Army Maj. Curt Kellogg said in a statement, reported AFP.

The head of the observatory, Rami Abdul Rahman, said that civilians still living in the village provided a list of names of the victims, which included 31 children and 19 women.

Kellogg told The Daily Beast that the U.S. works harder than any other military in the world "to be precise in the application of our airstrikes."

"We have significant mitigation measures in place within the targeting process and during the conduct of operations to reduce the potential risks of collateral damage and civilian casualties," Kellogg said. "I can assure you that before any mission, every precaution is taken to ensure civilians are not harmed. Our efforts stand in stark contrast to the tactics of [the Islamic State group], who continues to kill, torture, and abuse civilians as well as embed their combatants in civilian areas."

Despite the precautions, according to a report released in March by the Nobel Peace Prize-winning doctors' group Physicians for Social Responsibility, at least 1.3 million civilians, and as many as 2 million, have been killed in Iraq since the start of the U.S.-led "War on Terror." Another study from 2010 found dramatic increases in infant mortality, birth defects and cancer in Iraq, at rates greater than those found after atomic bombs were dropped on Hiroshima and Nagasaki in 1945.