Authorities in Pakistan briefly detained a U.S. Embassy employee Tuesday, after airport security officials found bullets in his luggage.

Officials say the American was about to fly from the northwestern Pakistani city of Peshawar to the capital, Islamabad, when he was taken into police custody.

He was released to the U.S. consulate after a few hours.

A U.S. official said the man was an embassy employee and had diplomatic immunity. The official said the U.S. Embassy was in contact with Pakistani authorities about the details of the case.

The presence of American personnel in Pakistan has been a sensitive issue since January of last year, when CIA contractor Raymond Davis was arrested in the eastern city of Lahore for the killing of two Pakistanis.

U.S. officials maintained that Davis had diplomatic immunity, but Pakistani authorities refused to release him for nearly two months.

The incident severely strained U.S.-Pakistan relations. Ties reached a new low last May when U.S. special forces killed al-Qaida leader Osama bin Laden in a Pakistani army town.