NEW YORK (Reuters) -- U.S. investigators say they have been combing through evidence in the hunt for suspects in a failed car bombing in New York's busy Times Square, and officials have expressed optimism that the culprits will be found.
New York Mayor Michael Bloomberg said there was no evidence of a link to Al-Qaeda or any other militant organization in the failed bomb attack on the evening of May 1 that prompted the evacuation of the teeming entertainment and shopping district.
"It's unfortunate that this happened. I'm confident that we will find out who did it," Bloomberg told reporters.
New York Police Commissioner Raymond Kelly said a white man in his 40s was spotted in security video footage and was seen removing a dark shirt about half a block from where the vehicle was left with its engine running and hazard lights flashing.
The Taliban in Pakistan said it planted the bomb to avenge the killing in April of Al-Qaeda's two top leaders in Iraq. But Kelly said there was "no evidence" to support that claim.
Investigators were poring over surveillance camera footage and a device made of propane, gasoline and fireworks after officers found the bomb in the vehicle as Times Square in Midtown Manhattan was packed with tourists and theater-goers.
President Barack Obama received regular updates on the incident as he visited Louisiana to assess the response to the huge oil spill in the Gulf of Mexico.
"We're going to do whatever is necessary to protect the American people, to determine who's behind this potentially deadly act and to see that justice is done," said Obama, who was accompanied on the trip by his counterterrorism chief John Brennan.
Homeland Security Secretary Janet Napolitano called the scare a "potential terrorist attack" but she and other officials held off saying whether there was a link to Islamist groups or to a domestic cause in the United States.