U.S. and Pakistani officials say the top U.S. intelligence official in Islamabad has returned home because of medical reasons.

The Central Intelligence Agency's station chief, who oversaw the intelligence team that found Osama bin Laden, is not expected to return.

The man cannot be named because he is undercover and the CIA has not commented on the matter.

It is the second time in seven months that the top U.S. intelligence officer has left the post in Pakistan. The previous station chief had to leave after a Pakistani official admitted that his identity had been leaked, causing a security breach.

Relations between the CIA and Pakistan's intelligence agency, ISI, have been strained since bin Laden was killed in a secret raid by U.S. special forces last May.