-LRB- CNN -RRB- -- Conflicting reports emerged Sunday about whether Adam Gadahn , a U.S.-born spokesman for al Qaeda , has been arrested in Pakistan . A senior Pakistani government official told CNN that Gadahn was arrested Sunday in Karachi , and a second senior Pakistani government official later confirmed the arrest . But a U.S. intelligence official said there appears to be no validity to the reports that Gadahn was in custody , and other U.S. officials also said they have no indication that Gadahn has been captured . Reports of the arrest came hours after Islamist Web sites posted video of Gadahn praising the November massacre at Fort Hood , Texas . On the video , Gadahn said the U.S. Army major charged with gunning down 13 people `` lit a path '' for other Muslim service members to follow . Gadahn , also known as Azzam the American , has routinely posted lengthy videos on Islamist online forums . In 2006 , he was indicted on charges of treason and providing material support to terrorists . The U.S. government has offered a $ 1 million reward for information leading to his capture . Authorities have targeted several key Islamist figures in Karachi , the populous port city and financial capital of Pakistan . For some time , it has functioned as a hideout for Taliban and al Qaeda sympathizers . One of the figures , top Taliban leader Agha Jan Motasim , was arrested on Friday . Motasim 's capture came on the heels of the arrest of the Taliban 's No. 2 figure and overall military commander , Mullah Abdul Ghani Baradar . Last month , Taliban and government sources confirmed that Pakistani Taliban leader Hakimullah Mehsud had died . A government official told CNN Mehsud died as a result of a January 14 unmanned drone attack in North Waziristan ; other sources said Mehsud died near the city of Multan in central Pakistan while on his way to a treatment center in Karachi . A city of 13 million -- with some estimates of 100,000 new arrivals a month -- Karachi as seen an influx of Pashtuns from the tribal border region with Afghanistan . Many fled there during fighting and offensives in the Northwest Frontier Province and Waziristan , making it a comfortable place for the Taliban to blend in and count on a network of supporters . `` I think its become apparent ... that al Qaeda does n't really have a base of sanctuary inside Afghanistan , at least not one where its leaders feel safe , '' CNN 's Senior International Correspondent Nic Robertson said . `` They 've taken to hiding inside Pakistan . '' Gadahn 's reported presence in Karachi `` is an indication of how easily it is for al Qaeda sympathizers and Taliban sympathizers to hide in that city , '' Robertson said . Gadahn , 31 , grew up on a California farm and was home-schooled until 17 . A year later he moved in with his paternal grandparents , who were secular Jews . He converted to Islam at the Islamic Society of Orange County , California , but was banned from the mosque two years later after hitting its chairman , Haitham Bundjaki . In 1997 Gadahn began working for a California charity suspected of having ties to al Qaeda . He moved to Pakistan in 1998 . His family has said they last heard from him in 2002 . In 2004 , the FBI identified him as part of an al Qaeda cell that was planning attacks aimed at disrupting that year 's presidential election in the United States . In October 2004 , he began appearing in disguise in al Qaeda videos . Gadahn dropped the disguise in 2006 . In 2008 , he renounced his U.S. citizenship and destroyed his passport in another al Qaeda video . In his video message posted online Sunday , Gadahn says Muslims should emulate the alleged Fort Hood shooter . `` I believe that defiant Brother Nidal is the ideal role model for every repentant Muslim in the armies of the unbelievers and apostate regimes , '' Adam Gadahn says in English in the video . Maj. Nidal Hasan , an Army psychiatrist and a U.S.-born citizen , is charged with 13 counts of premeditated murder in the November 5 killings . Hasan is also facing 32 counts of attempted premeditated murder and is eligible for the death penalty . `` The Mujahid brother Nidal Hasan is a pioneer , a trailblazer and a role model who has opened a door , lit a path and shown the way forward for every Muslim who finds himself among the unbelievers and yearns to discharge his duty to Allah and play a part in the defense of Islam and Muslims , '' Gadahn says in the video . Gadahn also cites in Sunday 's video the U.S. and allied buildup in Afghanistan , where the United States is in the process of adding about 30,000 troops . `` It is rapidly becoming clear that this already-hot global battle is about to get even hotter , '' he says . `` This is a war which knows no international borders and no single battleground , and that 's why I am calling on every honest and vigilant Muslim in the countries of the Zionist-Crusader alliance in general and America , Britain and Israel in particular to prepare to play his due role in responding to and repelling the aggression of the enemies of Islam . '' In December , Gadahn released a video message in English offering condolences to `` unintended Muslim victims '' killed in attacks in Afghanistan , Pakistan and elsewhere . It was a rare example of al Qaeda offering condolences to the families of those killed in the group 's own attacks . CNN 's Zain Verjee contributed to this report .