A source told CBS News it's becoming "increasingly plausible" that the Pakistani Taliban played some role in the Times Square bombing attempt.
The New York Times first reported on the mounting evidence of the groups involvement, which raises concerns about whether other militant groups could strike on U.S. soil.
It is unclear if the Pakistani-American accused of the failed Times Square car bombing was working alone when he began preparing the attack almost immediately after returning from his native land.
Two new surveillance videos emerged of the bomb suspect, Faisal Shahzad. Police told The Associated Press that one video shows him in a white baseball cap and a dark jacket walking away from the smoking, bomb-laden Nissan Pathfinder parked in the bustling heart of New York City.
The second video shows him buying a weak batch of fireworks in a store in Pennsylvania, according to the shop's owner.
Shahzad has told investigators that he trained in a terror camp and had contacts with members of the Pakistani Taliban. On Sunday, the Pakistani Taliban claimed credit for the attack, but since then U.S. officials have publicly and repeatedly said they have no proof of that.
Special Section: Terrorism in the U.S.
Shahzad faces terrorism and weapons charges after authorities said he admitted rigging the Pathfinder with a crude bomb of firecrackers, propane and alarm clocks based on explosives training he received in Pakistan. Authorities said he was cooperating with investigators and did not appear in Manhattan federal court for a second day.
Authorities indicated that Shahzad, the 30-year-old son of a retired air force official in Pakistan, had launched the bomb plot alone almost immediately after returning to his Connecticut home in February from the visit to his native land.
He did a dry run three days before trying to detonate the car bomb, said a law enforcement official who spoke to the AP on Wednesday on condition of anonymity because of the sensitive nature of the investigation.
Shahzad drove the SUV to Times Square from Connecticut on April 28, then returned to the scene April 30 to drop off a different vehicle, the official said. He then went back Saturday to leave the SUV with the car bomb but forgot the keys for both vehicles in the SUV and had to take public transit away from the area, the official said.
New York Police Commissioner Raymond Kelly told a Senate panel that Shahzad bought the gun found in his car at Kennedy Airport in March, when he appeared to move ahead on the bombing plot.
"It appears from some of his other activities that March is when he decided to put this plan in motion," Kelly said. "He came back from Pakistan Feb. 3, 2010. It may well have been an indicator of putting something catastrophic in motion."
Law enforcement officials in Washington said they had not verified statements investigators said Shahzad had made that he was trained in Pakistan for the attack. All the officials spoke on condition of anonymity to discuss the case.
The FBI was able to identify Shahzad's name because of information Customs and Border Protection officials shared months earlier, according to a law enforcement official who spoke on condition of anonymity to discuss the investigation.
When Shahzad returned from Pakistan in February, he went through extra screening at U.S. Customs because of rules put in place after the attempted terrorist attack on Christmas Day. Customs officials noticed Shahzad had traveled to Pakistan previously, but for weeks, instead of months like his most recent trip. Shahzad came back to the U.S. without his family and without a return plane ticket.
When Customs officials come across people with suspicious travel patterns such as these, they send information along to the FBI.
As the FBI was following leads from the SUV left in Times Square, they found a phone number in the records of a throwaway cell phone that Shahzad had used when he was buying the SUV in Connecticut. The number matched a phone number Shahzad gave to Customs officials when he returned from his last trip. The FBI then contacted Customs about the match, and Customs provided other travel information on the suspect.
Police recovered the video showing Shahzad in the baseball cap walking along Shubert Alley moments after witnesses saw the Nissan Pathfinder ditched Saturday in a no-standing zone across from a Broadway theater, a law enforcement official told the AP, speaking on condition of anonymity because of the ongoing investigation. Authorities were weighing whether to release the video.
Shubert Alley is the same spot seen in another video that was released by police on Sunday that shows a second man shedding his shirt near the SUV. The unidentified man was never referred to as a suspect but police had said they sought to interview him. Investigators don't believe he was involved in the attack, an official familiar with the probe told the AP.
The official said the video had the unintended effect of falsely reassuring Shahzad that he wasn't a target.
Interviews Wednesday with business owners shed light on a series of purchases Shahzad made of guns and fireworks near his Bridgeport, Conn., home and in Pennsylvania that authorities say proved a rapidly accelerating plot.
Shahzad is on video buying six to eight boxes each containing 36 Silver Salute M88 fireworks a consumer-grade product mostly made up of paper and cardboard - from Phantom Fireworks in Matamoras, Pa., on March 8, said store vice president William Wiemer.
Even if used together, the fireworks couldn't have caused a large explosion, Wiemer said.
"The M88 he used wouldn't damage a watermelon. Thank goodness he used that," said Bruce Zoldan, the company's president.
Each M88 has an amount of pyrotechnic powder that is less than 1/6 the size of an aspirin, the company said. Fireworks purchased illegally can be up to 1,000 times more powerful, they said.
"There's no doubt, had he bought this on the black market, that the outcome in New York would have been totally different," Zoldan said.
Shahzad had to show his driver's license and fill out an application to buy the fireworks, Zoldan said. On the form, "the individual put his last name first, and his first name last, probably intentionally," Zoldan said.
Police in Shelton, Conn., said Shahzad legally bought a Kel-Tech rifle from a dealer after passing a criminal background check and a 14-day waiting period. The owner of the gun shop declined comment.
Shahzad, who was charged Tuesday in the plot, was hauled off a Dubai-bound plane he had boarded Monday night at Kennedy Airport despite being under surveillance and placed on the federal no-fly list.
"I was expecting you. Are you NYPD or FBI?" Shahzad told Customs officials who came aboard the jet to arrest him, an official with knowledge of the investigation said.
The government said Wednesday it would require airlines to check no-fly lists within two hours of being notified of updates, after Shahzad was able to board his Emirates flight despite being placed on the list. The airline apparently failed to check the latest version of the terror watch list that included Shahzad's name.
Until now, airlines had been required to check for list updates every 24 hours.
Shahzad had fled to the airport after being spooked by news reports that said police were seeking a Pakistani suspect in Connecticut in the Times Square plot.
Two people familiar with the investigation, speaking on condition of anonymity because of the sensitivity of the case, said Shahzad slipped past federal surveillance Monday afternoon and drove to the airport, where his car was found with a gun inside.
Shahzad had previously lived in Shelton but got a low-rent apartment in nearby Bridgeport when he returned from Pakistan. Landlord Stanislaw Chomiak said Shahzad lived alone and he never saw him with anyone.
On Saturday night - after the failed bombing shut down Times Square for hours and panicked thousands of tourists - Chomiak said Shahzad called him and asked to be let into his building, saying he had lost his key.
Authorities said the Pathfinder that Shahzad left in Times Square had a chain of 20 keys left in the ignition, including the apartment keys.
"He said he was hanging out with a friend in New York and he must have lost the key somewhere," Chomiak said.
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