Investigators have the name of the courier who they believe helped Faisal Shahzad pay for the used sport utility vehicle and other materials to rig up a car bomb that would have caused a huge fireball in Times Square if it had gone off, the official told the AP. The official didn't know how much money may have changed hands.
The official spoke on condition of anonymity because of the sensitivity of the investigation.
U.S. law enforcement officials traveled to Pakistan - where Shahzad spent five months before returning to the U.S. in February - to question four alleged members of an al Qaeda-linked militant group. Investigators are trying to trace his movements in his homeland and looking into the possible financing of the operation between the Pakistan-born budget analyst and foreign terror groups.
Special Section: Terrorism in the U.S.
Shahzad, 30, who remains in custody on terrorism and weapons charges, lived alone in a Bridgeport, Connecticut, and rented an apartment with no apparent job since February. He is seen on videotape buying boxes of fireworks from a Pennsylvania store and authorities say he bought a rifle in Connecticut over the past three months with no apparent source of income.
He paid for the used SUV with 13 $100 bills, authorities say, then tried to blow up the vehicle in Times Square on Saturday. A T-shirt vendor saw smoke coming from the SUV and alerted police.
Officials have been investigating if Shahzad got money from militant groups, including the Pakistani Taliban, which originally claimed responsibility for the bombing attempt then backed off that claim.
Shahzad has claimed that he was angry about U.S. predator drone attacks on Pakistan, but investigators say financial pressures may have helped fuel his rage, reports CBS News correspondent Bob Orr. Sources tell CBS News Shahzad defaulted on his mortgage as well as another $60,000 equity loan.
Pakistan Interior Minister Rehman Malik said Friday he believed Shahzad did not act alone, but he had seen no evidence suggesting the Pakistan Taliban were involved.
"All those leads, suggesting it was his own action, I will not accept that. I'd like to see details," Malik told reporters in Beijing. "Obviously, he had bought a vehicle filled with explosives. It looks a bit difficult (to say) that he's (working) alone."
A Pakistani Taliban spokesman said Thursday the group had nothing to do with the attempted bombing, but added: "Such attacks are welcome."
"We have no relation with Faisal. However, he is our Muslim brother," Taliban spokesman Azam Tariq told the AP in Pakistan by telephone from an undisclosed location. "We feel proud of Faisal. He did a brave job."
The group has never launched a successful terrorist attack against the United States.
More coverage of the Times Square Bomb Plot:
Shahzad Practiced Bomb Plot, Official Says
Authorities Lost Faisal Shahzad in Traffic
Shahzad: Number Cruncher to Terror Suspect
Bomb Suspect Shahzad Seen Walking Away in Video
How You End Up on the U.S. No-Fly List
Shahzad Bought Weak Fireworks, Store Owner Says
Since his arrest Monday, Shahzad admitted to the failed bombing and has cooperated in the investigation, authorities say. He has not yet appeared in court.
Still, police Commissioner Raymond Kelly said investigators want to find out if "what he's saying is in fact the truth."
"We are directly looking at who did he have contact with while in Pakistan, what did he do, who is supporting him and why," State Department spokesman P.J. Crowley said.
In Karachi, Pakistan, both U.S. and Pakistani officials questioned four alleged members of the Jaish-e-Mohammad militant group, two Pakistani security officials told the AP, speaking on condition of anonymity because they were not authorized to speak to the media. The militant group is believed to have been established by Pakistani intelligence agencies, and has been linked to the al Qaeda terror network and the 2002 killing of Wall Street Journal reporter Daniel Pearl.