As Times Square returned to business as usual Friday, police released a photo of the bicycle, looked at dozens of security videotapes and scoured the area for possible witnesses.
"We're doing the normal investigative steps that you would expect in a case like this," Police Commissioner Raymond Kelly told CNN.
Among the videos were one showing a cyclist pedaling toward an area where the blue bicycle was found ditched in the trash and another with someone walking away from the same spot, police said.
They released a photo of the blue bike - a 10-speed in good condition - along with a surveillance-camera image of the hooded cyclist.
Witnesses to the explosion described seeing a hooded man on a bike acting suspiciously.
The bomb, contained in a metal ammunition box, produced a sudden flash and a billowing cloud of white smoke, prompting a full-scale emergency response.
Authorities said there was no connection between the blast and a letter sent Thursday to as many as 100 members of Congress bearing the words "Happy New Year, We Did It."
Officials said the lengthy anti-war letters - sent to congressional offices with photos of a man standing in front of the recruiting office before it was damaged - contained no threats.
One law enforcement official said the "We Did It" referred to Democrats taking control of Congress in 2006.
At Times Square on Friday, there were tourists snapping pictures, pedestrians bustling about - and a sense of firm resolve among the members of the military who were guarding the mangled recruiting station, located in the middle of a traffic island.
"The barricades were up around the whole island, and they were still asking about joining," Staff Sgt. Ruben Vila said.
Jessica Lindsey, 30, of Pensacola, Fla., paused for pictures with friends in front of the recruiting station during their shopping expedition and birthday celebration.
"We were nervous about coming here and staying across the street," but hotel workers assured them everything was fine, she said.
The blast bears striking similarities to the two previous small explosions at consulates in Manhattan.
In October, two small explosive devices were tossed over a fence at the Mexican Consulate, shattering windows. Police said they believed someone on a bicycle threw the devices.
At the time, police said they were investigating whether the blast was connected to a nearly identical bombing at the British consulate on May 5, 2005. No one was arrested in either incident.
