The U.S. military killed dozens of people in Syria, including women and children, in airstrikes conducted during the final days of the war against the Islamic State, but did not disclose its actions for more than two years, defense officials said Sunday.

The attacks on Baghouz, along Syria’s border with Iraq, were carried out March 18, 2019, after Syrian forces allied with the United States requested assistance and nearby U.S. troops reported seeing no civilians in the area, Navy Capt. Bill Urban, a U.S. military spokesman, said in a lengthy statement. The United States determined that at least 16 Islamic State fighters and four civilians were killed, he said.

But the U.S. military was “unable to conclusively characterize the status of more than 60 other casualties,” Urban said. That group, Urban said, included “multiple armed women” and “at least one” armed child.

“Likely a majority of those killed were also combatants at the time of the strike, however, it is also highly likely that there were additional civilian casualties,” Urban said.

Details of the strike were not disclosed until Saturday, when the New York Times published a report saying that some U.S. officials — including military and CIA personnel — had questioned the strike’s legitimacy, whether it constituted a war crime, and if there was a deliberate effort to hide the truth about what happened. The Times reported that military officials sought to conceal the strike, and that multiple investigative reports scrutinizing what had happened were “delayed, sanitized and classified.”

A U.S. military official, speaking on the condition of anonymity because of the issue’s sensitivity, said that the units involved — including elite personnel from the Army’s 5th Special Forces Group — quickly reported the possibility of civilian casualties internally.

For reasons that remain unclear, U.S. Central Command, which oversees military operations in that region, never released any details about the incident, this official said. The military did not explain why the strike was not disclosed until now, nor did it address whether the incident will be reviewed or if there are other similar cases that remain undisclosed.

Pentagon spokesman John Kirby said in an email Sunday that the Defense Department and Defense Secretary Lloyd Austin take seriously “the obligation to avoid civilian harm” in military operations.

“Without speaking to this specific event or any potential future decisions, Secretary Austin remains focused on making sure we do everything we can to both prevent these tragic outcomes and to be as forthcoming as we can be about them,” Kirby said.

The airstrikes occurred near the Euphrates River in the southeastern Syrian province of Deir al-Zour, where Syrian forces aligned with the United States sought to end the multiyear war with the Islamic State. The terrorist group made a last stand, and “multiple entreaties to ISIS to allow family members to depart the area were rebuffed,” Urban said.

The day of the incident, the Islamic State before dawn attacked U.S.-backed Syrian fighters using rocket-propelled grenades, suicide bombings and small arms, Urban said. Numerous U.S. aircraft conducted airstrikes and departed the area after depleting their weapons.

About 10 a.m., the Syrian forces called for help saying they were in danger of being overrun, Urban said. A U.S. drone remained overhead, but it was out of missiles and “unable to discern any civilians in the area.”

The only remaining coalition aircraft that could assist was an F-15E. It dropped three 500-pound bombs, U.S. military officials said.

Urban said that after the airstrikes, a coalition drone operator who was watching the situation on high-definition, full-motion video reported the possibility of civilian casualties. U.S. Special Operations troops who relayed the request for airstrikes “did not have access to their feed,” he added.

A U.S. military investigation concluded that the airstrikes were legitimate in defense of the U.S.-backed Syrian fighters on the ground, and proportional because of the unavailability of smaller bombs or missiles at the time, Urban said. The investigation recommended requiring high-definition video for similar strikes in the future.

An investigating officer determined that no discipline was warranted, Urban said.

“It is important to understand that ISIS decided to put their own families at risk when all avenues of escape were afforded to them,” Urban said. “It is also important to note that some women and children, whether through indoctrination or choice, decided to take up arms in this battle and as such could not strictly be classified as civilians.”

Correction: A previous version of this story misidentified the munitions U.S. forces used to conduct airstrikes on Baghouz, Syria, on March 18, 2019. All three were 500-pound bombs, according to U.S. Central Command, which released a statement Nov. 16 correcting inaccurate information it distributed initially. The article has been corrected.