The U.S. military said late Wednesday that civilians “were likely killed” during a Navy SEAL raid in Yemen on Saturday, a ground operation that erupted into a massive firefight that also took the life of an American sailor.

A statement issued by the U.S. Central Command said that an investigatory team “has concluded regrettably” that an unspecified number of civilians “appear to have been potentially caught up in aerial gunfire that was called in to assist U.S. forces” that were “receiving fire from all sides.”

Media reports from the region said that at least 10 Yemeni women and children were killed in the raid, the first counterterrorism operation authorized by President Trump.

[In deadly Yemen raid, a lesson for Trump’s national security team]

“You never want to call something a success 100 percent when someone’s hurt or killed,” White House press secretary Sean Spicer said Wednesday, referring to the death of Chief Special Warfare Operator William “Ryan” Owens, whose remains arrived Wednesday at Dover Air Force Base. Trump traveled to the Delaware base for the ceremony.

The speed with which the military acknowledged the civilian deaths was in stark contrast to the investigations after most previous allegations of civilian casualties, which have often taken months, if not years.

The goal of the operation was to detain Yemeni tribal leaders allegedly collaborating with al-Qaeda in Yemen and to gather intelligence about the group. Instead, a massive firefight ensued that brought in U.S. aircraft to strike the fighters and rescue the military team.

One of the aircraft, an MV-22 Osprey from a U.S. naval ship offshore, lost power and hit the ground hard enough to disable it and wound two service members. The $70 million aircraft was then intentionally destroyed by a U.S. bomb to ensure that it did not fall into militant hands.

The Central Command statement said that “determined enemy” forces “included armed women firing from prepared fighting positions,” and U.S. special operators were fired on from houses and other buildings.

“Al-Qaeda in the Arabian Peninsula has a horrifying history of hiding women and children within militant operating areas and terrorist camps, and continuously shows a callous disregard for innocent lives,” Central Command spokesman John J. Thomas said in the statement. “That’s what makes cases like these so especially tragic.”

The statement also said that “the raid resulted in the seizure of materials and information that is yielding valuable intelligence to help partner nations deter and prevent future terror attacks in Yemen and across the world.”

Although U.S. forces have conducted airstrikes against al-Qaeda in Yemen in recent years, the operation was the first U.S.-led ground raid in Yemen since 2014.