(Shakil Adil ~ Associated Press)
U.S. and Pakistani authorities are trying to trace the movements of the suspect, Faisal Shahzad, during his recent five-month stay in Pakistan. They are seeking to establish whether he connected with any of the myriad Islamic terrorist groups and received instructions, funding or training.
Shahzad faces terrorism and weapons charges in New York after authorities said he admitted rigging a sport utility vehicle with a crude bomb of firecrackers, propane and gasoline based on explosives training he received in Pakistan. U.S. authorities said they have yet to establish a firm link between Shahzad and an extremist group.
Early morning prayers had just finished Tuesday when authorities detained Mohammed Rehan as he left the Bathha Mosque. The compound -- surrounded by 10-foot walls concealing a multistoried madrassa -- is run by the Islamist militant group, Jaish-e-Mohammed, which is affiliated with al-Qaida.
"They arrested him after dawn prayers at the corner. They were waiting," said Alamgir, a witness who spoke to The Associated Press outside the mosque.
Three other people, also with suspected ties to Jaish-e-Mohammed, were picked up elsewhere in this teeming port city of 16 million people, according to Pakistani officials who spoke on condition they not be identified because they were not authorized to release information to the media.
One official said the men were being held at a "safe house" in Karachi where they were being interrogated by both U.S. and Pakistani officials. A second official also said the United States was involved in the interrogation.
Pakistan and the U.S. are close -- if sometimes uneasy -- allies, and CIA officials have been known to question al-Qaida and other terrorist suspects.
"It's an open secret that the FBI and CIA has a direct line to Pakistani intelligence," said one senior Pakistani security official who spoke on condition of anonymity because he did not have permission to speak to the media.
In Washington, State Department spokesman P.J. Crowley said the U.S. would be seeking specific help from Pakistan as the investigation into Shahzad develops.
"We are directly looking at who did he have contact with while in Pakistan, what did he do, who is supporting him and why," Crowley said.
A senior State Department official said the administration would be asking Pakistan to take "significant" actions based on what Shahzad has been telling investigators about his visits to the country. The official spoke on condition of anonymity because the requests have not yet been made.
Jaish-e-Mohammed operated terrorist training camps in Afghanistan during the Taliban regime, and the Bathha mosque belonged to the organization, police and intelligence officials said.
One of the officials said Rehan may have traveled with Shahzad to Peshawar, a main jumping-off point to the Afghan border region.
Another extremist group, the Pakistan Taliban, said Thursday it had no links with Shahzad and learned only through the media that he had told U.S. authorities of his training in a militant camp in Waziristan.
"We do not know about that," said Pakistani Taliban spokesman Azam Tariq, speaking by telephone to the AP from an undisclosed location.
The group has previously claimed responsibility for Saturday's failed attack in a video released Monday before Shahzad's arrest.
"We have nothing to do with his activities in previous days in America. We have no relation with Faisal. However, he is our Muslim brother," Tariq said.
"Such attacks are welcome and we feel proud of Faisal. He did a brave job," Tariq added.
It was not clear why the group would now deny having links to Shahzad. Two possible explanations could be that a faction of the group had links with the Shahzad, or that it is seeking to avoid a possible military offensive in its stronghold in north Waziristan by distancing itself from the act.
Another security official told the AP that Masood Azhar, the leader of Jaish-e-Mohammed, had come first to the Bathha mosque after being freed from an Indian jail in 1999 in exchange for an Indian Airlines plane hijacked to southern Afghanistan, where the Taliban were then headquartered.
Azhar was freed along with two other militants, including Sheikh Omar, who was later involved in the beheading of Wall Street Journal reporter Daniel Pearl. Omar is on death row in a Pakistani prison convicted of Pearl's death. The men met al-Qaida leader Osama bin Laden in Kandahar before leaving Afghanistan for Pakistan.
Neighbors of the Bathha Mosque said Azhar makes regular visits and was there in recent months. One neighbor, who refused to be identified citing personal safety concerns, told the AP that calls for violence accompanied the rallies that were sometimes attended by men with weapons.
"Whenever (Azhar) comes, there are large crowds and everyone in the neighborhood is afraid," the neighbor said from behind a high wall, refusing to step outside and running a finger across the throat to explain what might happen otherwise.
In his native village of Mohid Banda, retired air force Col. Abdul Aziz, a close friend of Shahzad's family, told the AP "he must have been brainwashed by (extremists) because he was such an obedient jovial young man."
Aziz served with Shahzad's father, who was a vice marshal in the Pakistani air force. Shahzad's parents, who have been living in the northwest border town of Peshawar, have not been seen by the media since news of his arrest broke.
Shahzad's father has been taken into protective custody by Pakistan's main intelligence agency, an agent from the organization said. The father was not considered a suspect and was being questioned about his son's activities, the agent said.
The agent spoke on condition of anonymity because the agency does not allow operatives to be identified in the media.
The family home is in a posh suburb of Peshawar hidden behind giant steel gates and large walls that hide the occupants from prying eyes. In conservative northwestern Pakistan, homes are traditionally obscured by high boundary walls.
Most of the homes in the Hayatabad suburb of Peshawar also are protected by guards.
As the son of an air force officer, Shahzad's childhood was spent traveling throughout the country.
He received his first passport in 1995 when he was 16 and living in Karachi, where his father worked with the Civil Aviation Authority after retiring from the air force.
Shahzad spent his formative years in Karachi, leaving in 1999 for the United States, where he married an American of Pakistani descent, officials said. His wife and two children are believed to be in Pakistan, but they have gone underground since Shahzad's arrest.
Associated Press Writer Rasool Dawar in Mir Ali contributed to this report.