NEW YORK - A day before driving an SUV with a rigged homemade bomb into Times Square, a Pakistani-American made a test drive into the heart of the city, dropped off a getaway car blocks from his target and took a train home to Connecticut, a law enforcement official told The Associated Press.

The official's account of Faisal Shahzad, who took no visitors in the shabby apartment where he hoarded a gun and low-grade fireworks for months, bolsters a growing theory that he prepared a terrorist attack in the United States on his own once he moved back to the U.S. from five months in his native Pakistan, law enforcement officials say.

But while no other suspects have been identified in the U.S., federal authorities are seriously investigating whether foreign groups in Pakistan or elsewhere financed the 30-year-old ex-budget analyst's failed terrorist plot against New York, two law enforcement officials have told the AP.

One of the officials, speaking on condition of anonymity because of the sensitivity of the investigation, has said one funding source under investigation is the Pakistani Taliban, which claimed responsibility for Saturday's botched bombing.

In Pakistan on Thursday, security officials said U.S. law enforcement officers have joined them in questioning four alleged members of another militant group, Jaish-e-Mohammad, which has been linked to the 2002 killing of Wall Street Journal reporter Daniel Pearl, over possible links to Shahzad. The security officials also talked to the AP on condition of anonymity because they were not authorized to speak to the media.

Pakistan's ambassador, Husain Haqqani, said Wednesday in Massachusetts that an investigation into Shahzad's links to Pakistan was inconclusive so far. "I think it's premature to start identifying groups and individuals with whom he might have trained," he said.

Shahzad, of Bridgeport, Conn., remained in custody on terrorism and weapons charges, accused of trying to detonate a crude bomb of gasoline, propane and low-grade fireworks on a crowded Saturday night in Times Square.

Officials said he has been cooperating with investigators since he was pulled off a Dubai-bound plane in New York on Monday.

Attorney General Eric Holder told a Senate hearing Thursday that Shahzad has continued to answer questions after being read his constitutional rights, rejecting criticism that reading Shahzad his Miranda rights hindered investigators.

"There is simply no higher priority than disrupting the potential attacks and bringing those who plot them to justice," Holder said.

Police Commissioner Raymond Kelly on Thursday said that the investigation was still in its beginnings, and that authorities were talking to Shahzad to determine if "what he's saying is in fact the truth."

Authorities investigating the failed attack have said that Shahzad made quick preparations to buy supplies for the homemade bomb, including the used SUV for which he shelled out 13 $100 bills a week earlier.

Kelly said Wednesday that Shahzad bought a gun in March that was found in his Isuzu at Kennedy Airport, suggesting that he was moving ahead with the bombing plot shortly after returning from Pakistan.

"It appears from some of his other activities that March is when he decided to put this plan in motion," Kelly told a Senate panel. "It may well have been an indicator of putting something catastrophic in motion."

A relative in Pakistan said Wednesday that Shahzad had been talking about the problems of Muslim in Iraq and Afghanistan on his last visit to Pakistan, and that his sensibilities had changed over several years in the U.S.

"When he was here, he was not religious-minded. But he was when he came back from the United States," said Nasir Khan, a relative in the family's ancestral village of Mohib Banda in northwest Pakistan.

U.S. officials have said they are been unable to verify whether Shahzad trained to make bombs at a terrorist camp in Pakistan, which Shahzad told authorities he did, according to the federal complaint against him.

Kevin Barry, a retired member of the New York Police Department's bomb squad, told the AP the design of the Times Square car bomb - which included fertilizer and an improvised fireworks-and-powder detonator - showed Shahzad had sufficient training to understand the basics of rigging an explosive device. But the bomb, which included fertilizer that was incapable of exploding, was a failure.

"He was trained, but he certainly didn't graduate at the top of the class," said Barry. "He had the design and the idea."

Officials have said the gray 1993 Nissan Pathfinder loaded with firecrackers, gasoline and propane could have created a huge fireball and killed nearby tourists and Broadway theatergoers if it had gone off successfully.

Shahzad first drove the Pathfinder to Times Square from Connecticut on April 28, apparently to figure out where would be the best place to leave it later, according to a law enforcement official who briefed a reporter on the dress rehearsal. He then returned April 30 to drop off a black Isuzu, the official said.

When he left Times Square on Saturday, he discovered he left a chain of 20 keys including those to the getaway car and his home in Connecticut in the SUV, and had to take the train home, the official told the AP.

Investigators had already started searching for suspects, when he returned to the scene on Sunday with a second set of keys to pick up the Isuzu, parked about eight blocks from the car bomb site, the official said.

In a city still jittery from the failed car bomb, an Emirates flight was pulled back to the gate at Kennedy on Thursday after a passenger's name was spotted and mistakenly thought to be someone on the no-fly list. Two people were taken off and then put back on the Dubai-bound plane, days after Shahzad was taken off his planned flight, on the same airline and to the same destination, officials said.

The night before, a truck abandoned near a toll booth to the Robert F. Kennedy Bridge caused alarm late Wednesday when a bridge authority officer believed he smelled gasoline coming from it and saw a man flee the truck. But the truck turned out to be empty and not a threat, police said.