The man accused in a failed car bombing in New York City made a practice run of the operation three days before he allegedly tried to detonate explosives in Times Square, according to a law enforcement source.

This undated photo from the social networking site Orkut.com shows a man who was identified by neighbours in Connecticut as Faisal Shahzad. (Orkut.com/Associated Press)

Faisal Shahzad drove a Nissan Pathfinder SUV from Connecticut through Times Square on April 28 to stake out locations to park for the planned attack last Saturday evening, an official close to the investigation told The Associated Press.

The official said Shahzad then returned April 30 with an Isuzu — to be used as a getaway vehicle — and parked it eight blocks from the intended bomb site.

However, he was forced to take the train back to Connecticut because he forgot the keys for both vehicles inside the SUV, the official said.

Investigators had already started searching for suspects when Shahzad returned to the scene Sunday with a second set of keys to pick up the Isuzu.

Street vendors had spotted the Pathfinder idling on West 45th Street on May 1. Police soon arrived and found it to be rigged with a crude bomb that didn't go off, reportedly because the fireworks in the SUV weren't the kind that ignite one another.

Scares on bus, JFK flight

There was a case of jittery nerves in New Hampshire on Thursday in light of Shahzad's arrest earlier in the week.

A police bomb squad was called to evacuate a Greyhound bus and nearby buildings in downtown Portsmouth after someone called 911 and reported an explosive device on board.

There was no immediate word whether police found anything suspicious.

Elsewhere, authorities detained two passengers aboard an Emirates airlines plane Thursday at New York's Kennedy Airport after spotting a name similar to one on the "no-fly" list.

The man and woman who were ordered off the Dubai-bound plane were allowed to return after officials determined there was no security threat.

On Wednesday night, police closed one of New York City's major bridges for a couple of hours after a man abandoned a rental truck reportedly smelling of gasoline.

On Monday, Shahzad, 30, was pulled off a plane headed for Dubai. He faces terrorism and weapons charges and has allegedly told investigators he received explosives training in Waziristan, a stronghold of the Pakistani Taliban.

Court documents filed in New York said Shahzad returned to the United States on Feb. 3 on a one-way ticket from Pakistan, where he had spent five months visiting his parents.

With files from The Associated Press