In what could be a major break in the Boston Marathon bombings case, a city politician says investigators are on the hunt for a man seen in a department-store surveillance video dropping off a bag at the site of Monday's bombings.

A law enforcement official confirms that authorities have found an image of a potential suspect but don't know his name.

City Council President Stephen Murphy says investigators saw the image on surveillance footage they got from a nearby department store, and that police officers involved in the probe say investigators have matched information from the surveillance footage with witness descriptions of someone leaving the scene.

Murphy says officers are chasing leads that could take them to the man.