KARACHI, Pakistan -

Police in Pakistan say they are questioning an American after U.S. authorities said an FBI agent had been arrested.

Pakistani police officer Rao Anwaar declined to say Wednesday whether the detained American was the FBI agent. Anwaar says investigators haven't received any written evidence proving the man worked for the U.S. Embassy in Pakistan.

Anwaar says the American arrived in Karachi on May 1 and was detained Monday when he was about to board a flight for Islamabad. He says officials found him carrying ammunition and three knives, as well as electronic devices that are being examined.

A law enforcement official in the U.S. identified the man as an FBI agent who is assigned to the FBI Miami Field Office, and said he was in Pakistan as part of a multi-agency, anti-corruption program.

Pakistani authorities confirmed the person was being held on anti-terrorism charges.

On Tuesday, a judge ordered that the agent be detained until at least Saturday so Pakistani security officials can investigate the matter.