WASHINGTON — U.S. special operations forces launched a rescue mission to retrieve two men kidnapped by insurgents in Afghanistan last month, but the hostages were not there when the rescue team arrived, U.S. defense officials said Thursday.

Pentagon press secretary Peter Cook said the rescue mission was approved by Defense Secretary Ash Carter and authorized by President Barack Obama. Cook said no U.S. personnel or civilians were injured and added he would not provide any more details “in order to protect the safety of hostages and operational security.”

According to defense officials, the mission was delayed one day because of questions about the intelligence and whether the hostages, an American and an Australian who worked at the American University of Afghanistan, were there. Officials would not provide the precise timing or location of the rescue attempt because they said it could jeopardize any possible future operations.

The officials said U.S. commandos killed seven enemy fighters at the location. They said based on interviews with people at the site it’s still not clear if the hostages were ever there.

The officials were not authorized to discuss the matter publicly, so spoke on condition of anonymity.

The two men were kidnapped as they traveled from the university to their home in Kabul last month.