A U.S. military investigation into a strike at a girls’ school in Iran has been “complex” given that it was located on an active Iranian cruise missile base but the probe is approaching its conclusion, a U.S. military commander said on Tuesday.

Reuters first reported that an initial, internal U.S. military investigation showed U.S. forces were likely responsible for the fatal strike in Minab. The Pentagon has since elevated the probe but it has not acknowledged any preliminary findings.

The incident took place on February 28 on the first day of the conflict and killed more than 175 children and teachers, Iranian officials say.

“I’m always reluctant to put a timetable on it. (The investigation) is coming to the end and I think transparency is important,” U.S. Admiral Brad Cooper, head of Central Command, testified on Tuesday before a committee in the U.S. House of Representatives.

Democratic lawmakers pressed Cooper to publicly acknowledge the likely U.S. responsibility.

“It’s really pretty clear what happened there. But 80 days on, we have not taken responsibility for that attack,” said U.S. Representative Adam Smith, top Democrat on the House Armed Services Committee.

Smith noted past examples of errant U.S. strikes and how the Pentagon would accept initial responsibility ahead of the completion of its investigation.

But Cooper suggested the school strike was different.

“The school itself is located on an active IRGC cruise missile base. It’s more complex than the average strike,” he told Smith.

Archived copies of the school’s official website show the school is adjacent to a compound operated by the Islamic Revolutionary Guard Corps, the military force that reports to Iran’s supreme leader.

Reuters, citing sources familiar with the matter, has reported that U.S. officials responsible for creating targeting packages appeared ​to have used out-of-date intelligence.

Law of War

Cooper said the U.S. military never targets civilians and said it would follow the law of war “to a T.”

Republican lawmakers asked Cooper for details on Iran’s alleged attacks on civilians, both inside Iran and throughout the Middle East.

Iranian authorities killed thousands of people during anti-government protests in January, Iran’s worst domestic unrest since the era of its 1979 Islamic Revolution. Rights groups say the government has continued to ​crack down on opponents while war rages.

Cooper estimated that Iranian security forces have killed tens of thousands of civilians inside Iran since late last year. Since the April 8 ceasefire, Iran has hanged dozens of people, Cooper said.

Cooper also said Iran had intentionally struck civilian areas throughout the Middle East over a thousand times since the conflict started in February, killing at least 300 civilians.

(Reporting by Phil Stewart and Patricia Zengerle; Editing by David Gregorio)