Islamabad , Pakistan ( CNN ) -- The identity and nationality of an alleged al Qaeda operative arrested in Pakistan remained shrouded in mystery and conflicting information Monday , a day after Pakistani officials said one of the FBI 's most wanted terrorists was in custody . A Pakistani military official said Monday that the man arrested is a foreign operative linked to al Qaeda . The official did not specifically describe the man as American and gave no further details . On Sunday , a senior Pakistani government official said that Adam Gadahn , a U.S.-born spokesman for al Qaeda , had been arrested . A second senior Pakistani government official later confirmed Gadahn 's arrest . But a U.S. intelligence official said there appeared to be no validity to the reports that Gadahn was in custody . Other U.S. officials also said they had no indication Gadahn had been captured . U.S. counterterrorism officials said Monday they had received no indication from Pakistan that any American had been arrested . One official said there was `` no validity '' to reports that Gadahn was arrested . Another called the reports `` bogus . '' News reports Monday cited Pakistani officials as saying that a different man , believed to be an American member of al Qaeda , had been arrested . But U.S. counterterrorism officials said the United States has not heard of the person , who was identified in some reports as Abu Yahya Mujahdeen al-Adam , an American born in Pennsylvania . One official said the reports coming out of Pakistan were a `` real head scratcher . '' Rick Snelsire , a spokesman for the U.S. embassy in Pakistan , said Monday that the embassy had not received any information about an American being detained by Pakistani security forces . Gadahn , 31 , also known as Azzam the American , was indicted on charges of treason and providing material support to terrorists in 2006 . The U.S. government has offered a $ 1 million reward for information leading to his capture . He is the first American charged with treason since 1952 . Reports of an arrest Sunday came hours after Islamist Web sites posted video of Gadahn praising a November massacre at Fort Hood , Texas . On the video , Gadahn said the Army major charged with gunning down 13 people `` lit a path '' for other Muslim service members to follow . Authorities have targeted several key Islamist figures in Karachi -- the heavily populated port city and financial capital of Pakistan that , for some time , has functioned as a hideout for Taliban and al Qaeda sympathizers . A city of 13 million -- with some estimates saying there are 100,000 new arrivals a month -- Karachi has seen an influx of Pashtuns from the tribal border region with Afghanistan . Many fled there during fighting and Pakistani military offensives in the Northwest Frontier Province and Waziristan , making Karachi a comfortable place for the Taliban to blend in and count on a network of supporters . CNN 's Reza Sayah , Nic Robertson and Adam Levine contributed to this report .
On Sunday , Pakistani military official said foreign operative linked to FBI arrested . Official did n't describe man as American , gave no further details . On Monday , officials from U.S. government said Azzam had been arrested . U.S. officials : Reports that Gadahn is in custody do n't seem valid , are a `` real head scratcher ''