Updated 10:31 p.m. ET
Two Pakistani officers and a government official said Sunday that an American charged with treason for working with al Qaeda had been captured, a development that could deliver another significant blow in the U.S.-led battle against the terror network.
U.S. defense, intelligence and law enforcement officials could not immediately verify the reported detention of Adam Gadahn, a 31-year-old spokesman for al Qaeda who has appeared on videos threatening the West, including one that emerged earlier Sunday.
The reported arrest of Gadahn follows the recent detention of several Afghan Taliban commanders in Karachi, including the group's No. 2. Those detentions have been seen as a sign that Pakistan, which has been criticized as an untrustworthy ally, was cooperating more fully with Washington.
Some observers were cautious about giving credence to the claim that Gadahn was in custody as reports emerged that the man arrested might instead be a Taliban militant leader. There was no way of independently verifying the arrest or identity, and detentions of terror suspects in Pakistan are often surrounded by conflicting reports.
CBS News was told by sources in the Pakistan government that it was Gadahn, even after U.S. officials refused to confirm it was the California native for whom a $1 million reward has been posted.
Later, CBS News' Farhan Bokhari in Islamabad reported that earlier reports the detained individual was Gadahn proved false. According to a Pakistan security official who spoke with CBS News on condition of anonymity, the arrested individual is in fact "a Taliban militant leader who is known as Abu Yahya."
The official said evidence compiled from an interrogation of the suspect and information exchanged with U.S. officials verified the man's identify.
The reassessment only added to the confusion surrounding the arrest of a man earlier described by other unnamed Pakistani security officials as Gadahn.
"In the light of our latest information, I can say, this is not looking like Gadahn. But it is still the arrest of an important Taliban militant," said the Pakistani security official who spoke to CBS News late Sunday.
Western diplomats in Islamabad, responding to the latest twist to this increasingly confusing saga, said the arrest is not insignificant. "Even if this is not Adam Gadahn, it is still not an unimportant development. But let's hold our breath before we come to a final conclusion. We may be groping in the dark 'til someone, especially the Pakistanis who are holding this man, agree to present him publicly," said one western diplomat in Islamabad who spoke to CBS News on condition of anonymity.
Gadahn, who is also known by various aliases (including Yahya Majadin Adams and Azzam al-Amriki), has posted videos and messages calling for the destruction of the West and for strikes against targets in the United States, the most recent surfacing today, in which.
Gadahn grew up on a goat farm in Riverside County, Calif., and converted to Islam at a mosque in nearby Orange County, before moving to Pakistan in 1998, where he is believed to have attended an al Qaeda training camp, and served as a translator and consultant for the group,
"If this is him, it's a big capture and a morale-booster," said Patrick Rowan, the former top anti-terrorism official in the Bush Justice Department.
Gadahn, the first American to face treason charges in more than 50 years, has appeared in more than half a dozen al Qaeda videos, taunting the West and calling for its destruction. The video that surfaced Sunday showed him urging American Muslims to attack their own country.
"It's a blow to al Qaeda and a boost to the U.S. when a guy that has been taunting the U.S. for years has been captured," Rowan said.
Gadahn was arrested in the sprawling southern metropolis of Karachi in recent days, two officers who took part in the operation said. A senior government official also confirmed the arrest, but said it happened Sunday. The discrepancy could not immediately be resolved.
They spoke on condition of anonymity because they were not authorized to release the information.
The intelligence officials said Gadahn was being interrogated by Pakistani officials. Pakistani agents and those from the CIA work closely on some operations in Pakistan, but it was not clear if any Americans were involved in the operation or questioning.
In the past, Pakistan has handed over some al Qaeda suspects arrested on its soil to the United States.
If the man in custody is indeed Gadahn and authorities can get him to talk, he could offer valuable intelligence about al Qaeda's second in command Ayman al-Zawahiri and maybe even Osama bin Laden, Rowan said.
Gadahn has been on the FBI's most wanted list since 2004 and there is a $1 million reward for information leading to his arrest. He was charged with treason in 2006 and faces the death penalty if convicted. He was also charged with two counts of providing material support to a designated foreign terrorist organization.
Gadahn grew up on a goat farm in Riverside County, California, and converted to Islam at a mosque in nearby Orange County.
He moved to Pakistan in 1998, according to the FBI, and is said to have attended an al Qaeda training camp six years later, serving as a translator and consultant. He is known by various aliases, including Yahya Majadin Adams and Azzam al-Amriki.
In the video posted Sunday, he praised the U.S. Army major charged with killing 13 people in Fort Hood, Texas, as a role model for other Muslims. It appeared to have been made after the end of the year, but it was unclear exactly when.
"You shouldn't make the mistake of thinking that military bases are the only high-value targets in America and the West. On the contrary, there are countless other strategic places, institutions and installations which, by striking, the Muslim can do major damage," Gadahn said, an assault rifle leaning up against a wall next to him.
Pakistan joined the U.S. fight against Islamic extremists following the Sept. 11 attacks, and several high-ranking al Qaeda and Taliban have been arrested. But critics have accused the country of not fully cracking down on militants, especially those who do not stage attacks in Pakistan, while receiving billions of dollars in U.S. aid.
Osama bin Laden is believed to be hiding somewhere in the country, most likely close to the Afghan border.
Al Qaeda has used Gadahn as its chief English-speaking spokesman. In one video, he ceremoniously tore up his American passport. In another, he admitted his grandfather was Jewish, ridiculing him for his beliefs and calling for Palestinians to continue fighting Israel.
Dawud Walid, the executive director of the Michigan chapter of the Council on American-Islamic Relations in Southfield, Michigan, condemned Gadahn's call for violence, calling it a "desperate" attempt by Al Qaeda's spokesman to provoke bloodshed within the U.S.
Walid, a Navy veteran, said Muslims have honorably served in the American military will be unimpressed by al Qaeda's message aimed at their ranks.
"We thoroughly repudiate and condemn his statement and what we believe are his failed attempts to incite loyal American Muslims in the military," he said.
Imad Hamad, the senior national adviser for the American-Arab Anti-Discrimination Committee, based in Dearborn, Michigan, condemned al Qaeda's message and said it would have no impact on American Muslims.
"This a worthless rhetoric that is not going to have any effect on people's and minds and hearts," he said.
A leader of the Southern California mosque where Gadahn once worshipped said he was relieved to hear about the possible arrest.
"We are grateful to God that one less headache is off our hands," said Haitham Bundakji, vice chairman of the Islamic Society of Orange County. "The less troublemakers there are at large, the less troubles there are for us at home."
The last person in the U.S. convicted of treason was Tomoya Kawakita, a Japanese-American sentenced to death in 1952 for tormenting American prisoners of war during World War II. President Dwight D. Eisenhower later commuted his sentence to life imprisonment.