An apartment in Bridgeport, Connecticut, was raided by FBI agents
Law enforcement officials in New York say Faisal Shahzad, a 30-year-old naturalised US citizen who had settled in the state of Connecticut, activated a plot to bomb the city's world-famous Times Square after returning from a five-month visit to his native Pakistan.
It is unclear what Mr Shahzad was doing in Pakistan.
One report says he spent time in Peshawar, a strife-torn city in an area of the country where the Taliban insurgency is at its strongest. Other reports suggest he may have been visiting his wife.
A senior Pakistani security source told the BBC that Mr Shahzad was not someone who had come to the attention of the authorities.
But he was quick to add: "You can't keep tabs on everyone in the Pakistani diaspora."
In early April, after returning to Connecticut, Mr Shahzad is said to have bought a 1993 Nissan Pathfinder Sports Utility Vehicle (SUV) from a resident of the state, paying cash.
High-sided, petrol-thirsty SUVs attract attention and occasionally hostility in Europe, but in the US they are very common - and unlikely to attract attention.
The bomb was relatively unsophisticated
Law enforcement officials say that on Saturday 1 May, Mr Shahzad drove the vehicle, laden with an explosive device designed to kill and maim, to Times Square in Manhattan, where he parked it near a theatre and left the scene.
The explosive device was made up of alarm clocks, fireworks, petrol tanks, propane tanks and fertiliser.
While experts believe the fertiliser was not a type volatile enough to explode, police say the bomb could have produced "a significant fireball" and created shrapnel with enough force to kill pedestrians and smash windows.
Taliban link discounted
A street vendor alerted police to the parked SUV after he saw smoke coming from the vehicle.
Times Square was evacuated and shut down for 10 hours as a bomb squad defused the explosive device.
The amateurish, unsophisticated nature of this failed attack led the US authorities to at first dismiss any link to international terrorism. A claim of responsibility by the Pakistani Taliban was quickly discounted.
But the possibility of an international angle was raised after Mr Shahzad's dramatic arrest at New York's JFK airport on the evening of Monday 3 May.
The suspect was removed from Flight EK202 as it prepared to take off for Dubai following a two-day investigation by the FBI, New York police and other agencies.
Speaking shortly afterwards, Attorney General Eric Holder said: "We will focus on not just holding those responsible accountable, but also on obtaining any intelligence about terrorist organisations overseas."