Eric Holder: "We will not rest until everyone responsible is brought to justice"
A man has been arrested in connection with the failed car-bomb attack in New York City on Saturday evening.
Faisal Shahzad, a US citizen of Pakistani origin, is due to appear in a Manhattan court later to face charges of driving the bomb into Times Square.
US Attorney General Eric Holder said Mr Shahzad was detained at John F Kennedy Airport in New York on Monday as he attempted to leave for Dubai.
Mr Holder said it was clear the bomb had been intended to kill Americans.
"This investigation is ongoing, as are our attempts to gather useful intelligence, and we continue to pursue a number of leads."
By Steve Kingstone, BBC News, Washington
The attorney general implied that there might be a foreign terrorist link.
He said that as well as trying to detain suspects and question them, his organisation would be trying to gather intelligence about overseas terrorist organisations.
That's a little bit different from what we've heard until now - the authorities had implied that this was a low-level and amateurish affair.
Officials said Mr Shahzad, who reportedly only became a naturalised US citizen last year, was believed to have recently bought the car that was found loaded with improvised explosives in the heart of Times Square.
The FBI said it had searched his house in Bridgeport, Connecticut, on Tuesday. They removed several filled plastic bags from inside.
US reports say the 30-year-old recently returned from a five-month visit to Pakistan. They say he was tracked for two days by investigators using evidence found in the vehicle and the unexploded bomb components.
Mr Shahzad has told investigators he acted alone, unnamed US law enforcement officials say. However, they are still exploring whether he or others who might have been involved had been in contact with people or groups overseas.
On Sunday, the Pakistani Taliban said it was responsible for the failed bombing attempt and it threatened suicide attacks on major US cities. US officials said they had no evidence to support the claims.
The BBC's Aleem Maqbool in Islamabad says soon after the news broke of Mr Shahzad's arrest, a senior Pakistani security source said he was "not surprised" by the connection with his country.
The bomb was discovered and dismantled before it could explode
But government officials also point out that this is not just a Pakistani security problem, it is an American one as well, he says.
There is scepticism among experts in Pakistan about a direct Taliban link, our correspondent adds. There are numerous militant groups, and potentially hundreds of people an individual could approach for militant training in Pakistan.
Meanwhile, Emirates Airlines said the US authorities had removed two other people from its flight to Dubai on Monday. It is unclear whether they were connected to Mr Shahzad.
"Full security procedures were activated, including the deplaning of all passengers and a thorough screening of the aircraft, passengers, and baggage," it said in a statement quoted by the AFP news agency.
The car containing a bomb made from fertiliser, fireworks, petrol and propane gas tanks was left in Times Square on Saturday evening.
The 1993 Nissan Pathfinder was parked with its engine running and hazard lights flashing.
Naturalised US citizen born in Pakistan
Resident of Bridgeport, Connecticut
Reports say he recently returned from five-month visit to Pakistan
The bomb was discovered and dismantled before it could explode after a street-vendor noticed smoke coming from the vehicle and alerted police.
Mr Holder told a news conference that investigators were pursuing several leads, adding: "We will not rest until we have brought everyone responsible to justice."
He urged the American people to "remain vigilant" and report anything suspicious to the authorities.
Mr Holder said the attempted car bombing "would have been a deadly attack had it been successful".
He added: "It's clear that the intent behind this terrorist act was to kill Americans."
Times Square was packed with tourists and theatregoers when the alarm was raised.
Police evacuated a wide area of the district and closed subway lines, while a controlled explosion was carried out.
Officials said the bomb was crude, but could have sparked a "significant fireball" and sprayed shrapnel with enough force to kill pedestrians and knock out windows.
Investigators initially focused on a man who was seen on one video walking away from the area where the car was parked. He looked over his shoulder at least twice and pulled off a shirt, revealing a red T-shirt underneath.
New York's police commissioner said investigators still wanted to speak to the man, but acknowledged that he might not be connected to the bombing attempt.
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