Investigators believe funding for Faisal Shahzad in the United States was channeled through an underground money transfer network known as "hawala," the officials said. But, one official told The Associated Press, "there's a belief that no one in the U.S. who got him the funds was aware of what they were for."
The Pakistani-American was the only person in the United States who was "operational" in the plot to attack Times Square with a crude gasoline-and-propane car bomb on May 1, the official said. The bomb did not explode and no one was hurt.
The officials spoke to the AP on condition of anonymity because the investigation has not been completed.
The attempted attack set off a massive probe involving hundreds of federal agents in several cities. Nearly three weeks later, investigators have so far concluded that once he was funded, Shahzad acted alone, the officials said.
Three men were arrested last week in New England on immigration charges as authorities followed the money trail. Authorities said they were suspected of providing money for Shahzad; a prosecutor said one had Shahzad's cell phone number and his first name written on an envelope in his apartment.
All have denied knowing anything about the plot.
"They have no connection to this man," Saher Macarius, a lawyer for two of the men, said Friday.
Federal prosecutors had no comment on Friday. There no immediate reply to a phone message left for Shahzad's lawyer.
The investigation's main asset has been Shahzad. After he waived his right to an initial court appearance and agreed to cooperate after his May 3 arrest, a special interrogation team of FBI, CIA and Defense Department investigators was brought in to grill him in a Brooklyn hotel room, an official said.
The team was there to "build his trust," the official said. "But he was never really worried about talking. It was clear from the start, he wanted to."
Shahzad told investigators he was "supported" by the Pakistani Taliban, which initially claimed responsibility for the bombing in three separate videos, then later denied any role.
U.S. Attorney General Eric Holder said earlier this month of the Taliban: "We know that they helped facilitate it; we know that they helped direct it. And I suspect that we are going to come up with evidence which shows that they helped to finance it."