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Pakistani-born U.S. citizen Faisal Shahzad has admitted trying to set off a car bomb in busy Times Square and will face terrorism and mass destruction charges, Attorney General Eric Holder said Tuesday.

Holder said in a press conference that Shahzad has been charged with an act of terrorism and attempted use of a weapon of mass destruction in the May 1 bomb plot.

Holder said Shahzad, who has provided "valuable information" to investigators, attempted to carry out a "lethal terrorist attack" aimed at "murdering Americans in one of the busiest places in our country."

Deputy FBI director John Pistole said Shahzad was placed on the No Fly list just hours before he was arrested Monday -- a key step in preventing him from fleeing the country on a flight to Dubai, he said.

Homeland Security Secretary Janet Napolitano said Customs and Border Protection officials at the airport ordered that the flight be stopped before takeoff. Napolitano said they were able to arrest Shahzad on the plane and turned him over to the FBI -- though she declined to say how he was able to board the flight if he was on the No Fly list.

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Authorities tracked down Shahzad using the vehicle identification number on the Nissan Pathfinder that failed to detonate. They linked that number to a recent sale in Connecticut, Holder said.

Click here to read the criminal complaint.

Holder said he could not confirm reports that between four and eight people have been taken into custody for questioning in Pakistan in connection with the bombing attempt.

CBS News reported earlier Monday that Pakistani authorities apprehended suspects connected to the terrorist plot during raids Monday night and Tuesday morning in different locations. Some of them may be related to Shahzad, according to the network.

Pakistani intelligence officials also told Fox News on Tuesday that a man was arrested in Karachi  for his connection to the bomb plot.

The reported capture comes after Shahzad was arrested as he came minutes away from fleeing the U.S. when his Dubai-bound flight was returned to its gate at New York's Kennedy Airport and U.S. officials escorted him from the plane, along with two other men.

Federal investigators at Shahzad's home have removed a fireworks box among other evidence at the property in Bridgeport, Conn.

The box is labeled "Silver Salutes." The fireworks are similar to the M88s authorities say were found among containers of gasoline and other materials left in an SUV meant to explode in Times Square.

Shahzad is scheduled to appear in court Tuesday to face charges that he tried to set off a massive fireball and kill Americans after parking his car on a street lined with restaurants and Broadway theaters, federal authorities said.

The U.S. attorney's office in Manhattan was handling the case against Shahzad, 30, but has not yet made the charges against him public. FBI agents searched the home at a known address for Shahzad in Bridgeport, Conn., early Tuesday, said agent Kimberly Mertz, who wouldn't answer questions about the search.

Authorities removed filled plastic bags from the house overnight in a mixed-race, working-class neighborhood of multi-family homes in Connecticut's largest city. A bomb squad came and went without entering as local police and FBI agents gathered in the cordoned-off street.

In all, three passengers were removed from Emirates Airline Flight EK202 late Monday night as Shahzad was taken into custody by FBI agents and New York Police Department detectives.

But Shahzad told investigators he acted alone and denied any ties to radical groups in his native Pakistan, a U.S. law enforcement official familiar with the investigation told Reuters.

Though Holder said Tuesday that Shahzad was identified by customs agents and taken into custody before boarding his flight, a representative for Emirates Airlines confirmed to Fox News that Flight 202 "was called back by the local authorities prior to departure," and that the three passengers who were removed had already boarded the plane.

"Full security procedures were activated including the deplaning of all passengers and a thorough screening of the aircraft, passengers, and baggage," the airline representative told Fox News. "Emirates is cooperating with the local authorities." The plane was delayed about seven hours and took off for Dubai at approximately 6:30 a.m. ET.

Shahzad is a naturalized U.S. citizen and had recently returned from a five-month trip to Pakistan, where he had a wife, according to law enforcement officials who spoke to The Associated Press on condition of anonymity because of the sensitivity of the investigation into the failed car bombing.

Law enforcement officials say Shahzad became a U.S. citizen in April 2009 and passed all the criminal and national security background checks required for citizenship.

The officials familiar with the inquiry say investigators plan to go through his citizenship application line by line to see if he lied about anything. He became a citizen in Hartford, Conn.

Shahzad was being held in New York overnight and couldn't be contacted. A phone number at a listed address for Shahzad in Shelton, Conn., wasn't in service.

Law enforcement officials say Shahzad bought the SUV, a 1993 Nissan Pathfinder, from a Connecticut man about three weeks ago and paid cash. The officials spoke to the AP on condition of anonymity because of the sensitive nature of the case.

The vehicle identification number had been removed from the Pathfinder's dashboard, but it was stamped on the engine, and investigators used it to find the owner of record, who told them he had sold the vehicle to a stranger.

As the SUV buyer came into focus, investigators backed off other leads, although Holder said U.S. authorities "will not rest until we have brought everyone responsible to justice," suggesting additional suspects are being sought.

The SUV was parked on Saturday night on a busy midtown Manhattan street near a theater showing "The Lion King." The explosive device inside it had cheap-looking alarm clocks connected to a 16-ounce can filled with fireworks, which were apparently intended to detonate gas cans and set propane tanks afire in a chain reaction "to cause mayhem, to create casualties," police Commissioner Raymond Kelly said.

A metal rifle cabinet placed in the SUV's cargo area was packed with fertilizer, but NYPD bomb experts believe it was not a type volatile enough to explode like the ammonium nitrate grade fertilizer used in previous terrorist bombings.

Police said the SUV bomb could have produced "a significant fireball" and sprayed shrapnel with enough force to kill pedestrians and knock out windows.

A vendor alerted a police officer to the parked SUV, which was smoking. Times Square, clogged with tourists on a warm evening, was shut down for 10 hours. A bomb squad dismantled the explosive device, and no one was hurt.

But Holder said Americans should remain vigilant.

"It's clear," he said, "that the intent behind this terrorist act was to kill Americans."

In Pakistan, Interior Minister Rehman Malik said authorities had not been formally asked for help in the probe.

"When the request comes, we will cooperate with the U.S. government," he told the AP.

The Pakistani Taliban appeared to claim responsibility in videos that surfaced after the weekend scare, monitoring groups said, but police had no evidence to support the claims.

More than a dozen people with American citizenship or residency, like Shahzad, have been accused in the past two years of supporting or carrying out terrorism attempts on U.S. soil, cases that illustrate the threat of violent extremism from within the U.S.

Among them are Army Maj. Nidal Hasan, a U.S.-born Army psychiatrist of Palestinian descent, charged with fatally shooting 13 people last year at Fort Hood, Texas; Najibullah Zazi, a Denver-area airport shuttle driver who pleaded guilty in February in a plot to bomb New York subways; and a Pennsylvania woman who authorities say became radicalized online as "Jihad Jane" and plotted to kill a Swedish artist whose work offended Muslims.

The Associated Press contributed to this report.