Two bombs ripped through the crowd at the finish line of the Boston Marathon on Monday, 15 April 2013. Law enforcement bodies are saying that the blasts were terrorism acts.

In the result of the blasts, three people died and about 150 people were wounded, according to official data.

Investigators found what could be five additional, undetonated explosive devices around the Boston area, the Wall Street Journal reported, citing two unnamed people briefed on the investigation.

The Boston Marathon has been held on Patriots Day, the third Monday of April, since 1897. The event, which starts in Hopkinton, Massachusetts and ends Boston’s Copley Square, attracts an estimated half-million spectators and some 20,000 participants every year.