NEW YORK, NY March 07, 2008 —Law enforcement officials now say that letters with the words "We did it" sent to lawmakers on Capitol Hill were from a war protester and not linked to the explosion.

Last night, WNBC reported a possible connection with an incident at the Canadian border last month in which four men tried to flee at a checkpoint, two successfully, leaving behind a backpack with photos of New York landmarks behind.

The NYPD is looking for a bicyclist, who private cameras show riding up to the recruiting station a few minutes before the blast. As the person bikes away, the explosion occurs.

Police Commissioner Ray Kelly says yesterday's attack bears a strong resemblance to bombings at the Mexican Consulate last year and at the British Consulate in 2005.

For WNYC, I'm Anni Katz.