An operative of Al Qaeda believed to be an American was arrested in the sprawling southern city of Karachi in recent days by Pakistani security officials, Pakistani officials said Sunday.  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. For hours, information was difficult to confirm from Pakistan. President Obama was briefed on news reports of the arrest, but later learned they were most likely not correct. – New York Times