Earlier in the day, a third explosion reported to have gone off at the JFK presidential library was caused by a fire, according to police. Two more explosives found in the area were diffused.
Investigators warned police to be on the lookout for a "darker-skinned or black male" with a possible foreign accent in connection with the attack, according to a law enforcement advisory obtained by CNN.
In addition, several reports said a Saudi national with a leg wound was under guard at a Boston hospital in connection with the bombings. However, investigators cannot say he is involved at this time and he is not in custody, a law enforcement official said Monday evening, the CNN report said.