The bicycle was found several blocks away from the Army recruiting station that was hit by a small device early Thursday morning, blowing out its window.
The 10-speed bike looked relatively new, but was nevertheless dumped in the trash at Madison Avenue and 38th Street and found by a building superintendent who called police.
"I don't think anyone was seen leaving the bike," said New York City Police Commissioner Ray Kelly.
The bomber is seen on a grainy surveillance tape riding into Times Square early Thursday morning, getting off the bike and walking over to the recruiting center. Moments later, there is an explosion.
Later Thursday, police scrambled to review letters that were received by about 10 members of Congress. The mailed packets included a long anti-war manifesto along with a photo of a man standing in front of the recruiting center with the words, "Happy New Year. We did it."
But police are beginning to discount whether the letters had anything to do with the bombing and believe they might be a bizarre coincidence.
The letters had a Los Angeles return address on them and police interviewed the man who lived at that address Thursday night. One thing that was clear is that the man was not in New York City early Thursday morning, sources said.
Of growing interest to investigators, however, is a stop made on the Canadian border about a month ago.
High level law enforcement sources told ABC News that the stop, made by Canadian authorities, has yielded evidence that may be linked to the bombing and that individuals are being sought in connection with the case.
Canadian authorities are not commenting on the matter either to confirm or deny.
But sources told ABC News that U.S. and Canadian authorities are reviewing the incident. When the vehicle was stopped for a border inspection, there were four people in the car, but one man jumped out and fled. A search of the car found photos of Times Square in a backpack.
The material was passed on to U.S. authorities at the time, but an investigation did not turn up any evidence of criminal activity. In light of Thursday's bombing the leads were being reinvestigated, sources said.
Police are also trying to determine whether the Times Square bombing is linked to two earlier incidents in which crude homemade bombs were tossed at the British and Mexican consulates.
In all cases the devices were tossed just before 4 a.m., black powder was used, there were no injuries and property damage was limited to broken windows, door frames and flower pots.
Most important is that in all cases a person was seen either casing the scene on a bicycle, tossing the devices from a bicycle or leaving the scene on a bike.
Pierre Thomas contributed to this report.
