Two explosions are reported to have occured near the finish line of this year's Boston marathon.
The area is closed off by security and people are reported to have been injured.
Witnesses reportedly heard two booms near the finish line inside the Fairmount Copley Plaza Hotel that sounded like two claps of thunder, says Fox News.
A reporter who ran at the marathon and spoke to the Boston Herald said from what he saw the explosives might have been planted in a trash bin.
The incident has been confirmed by local police.
The explosions went off around 3 pm local time, while there were still people finishing the marathon, and some three hours after the winners crossed the line.
Police and medics were seen transporting injured people, while helicopters were deployed to survey the area.