Police said on Monday that a third explosion hit the Boston JFK Library, but it remains unclear whether it was related to the previous two blasts near the finish line of the Boston marathon.

"There was a third explosion at the JFK library," Boston Police Commissioner Ed Davis said at a press conference, adding that he was not yet aware of any injury in the third explosion.

Davis announced a police tipline for information that could lead to the arrest of those who were responsible for the attacks. He also advised people to stay at home or in the hotel.

Meanwhile, U.S. media reports said that the number of those injured in the explosions has soared to over 100, with at least two deaths.