Pakistani officials did arrest an Al Qaeda operative who might be American, but it now looks like it wasn’t Adam Gadahn.

American and Pakistani officials said the man arrested was Abu Yahya Mujahdeen al-Adam, who was described as having been born in Pennsylvania and who was thought to be affiliated with the operations division of Al Qaeda, commanding fighters in Afghanistan.

One American official briefed on the arrest described the operative in custody as fair-skinned and someone who spoke both English and Pashto. Little else was known about him, American officials said, and it was not immediately clear that American officials were involved in the arrest. There was no confirmation that the arrested man was in fact an American.

Initial reports seemed to have confused him with Adam Gadahn, a California native who has been a Qaeda spokesman and often appears on videos calling for strikes against targets in the United States.

Senior administration officials said on Sunday that they did not believe the arrest was of Mr. Gadahn.