The U.S. military is investigating several “credible” allegations of civilian casualties in its airstrike campaign against the Islamic State in Iraq and Syria (ISIS), the Pentagon said Tuesday. 

“I know that they are actively investigating what they believe to be at least a few incidents of civilian causalities that they think, you know, warrant further investigation, that they have found credible to investigate,” said Pentagon press secretary Rear Adm. John Kirby on Tuesday. 

{mosads}The comments are the first time the Pentagon has acknowledged it is looking into such allegations during the war against ISIS. 

“This is something we always take seriously. We are very mindful of trying to mitigate the risk to civilians every time we operate, everywhere we operate,” Kirby added. 

“And so when we do believe that we’ve had occasion to cause collateral damage or hurt, kill civilians, we take it seriously and we look into it. It matters to us,” he said. 

Kirby did not specify who made the allegations or when, but said some were initiated by the military. 

Separately, he said “several hundred” ISIS fighters have been killed.

“In regards to civilian casualty allegations, there is no other military in the world that works as hard as we do to be precise,” added a spokeswoman from the coalition in a statement.

“When an allegation of civilian casualties caused by Coalition forces is determined to be credible, we investigate it fully and strive to learn from it so as to avoid recurrence,” she continued.

“That said, we are aware of claims of suspected civilian casualties related to Coalition airstrikes in Syria and Iraq and we continue to evaluate them.”

This story was updated at 6:08 p.m.