UPDATE 5:50
Obama to address nation on Boston Marathon explosions at 6:10 pm ET -White House (via @Reuters)
UPDATE 5:36
Secret Service expands security at White House following Boston Marathon explosions (via @MarcTDG)
UPDATE 5:32
UPDATE 5:19: Footage of the explosion (via Boston Globe)
UPDATE 5:08: Boston hospitals report more than 100 being treated after Marathon explosions. (via @BostonGlobe)
UPDATE 5:05: Cellphone service has been shut down in the Boston area to prevent any remote detonations (via @AP)
UPDATE 4:59: Boston FD: Many runners abandoned bags during explosion, all bags are being treated as possible explosives. (via Long Island Press)
UPDATE 4:57: Google has released a Google Person Finder site for the Boston Marathon explosion.
UPDATE 4:54: Boston Police saying third explosion happened 30 minutes ago at JFK Library. Not sure if related to first two explosions.
UPDATE 4:46: Boston Globe reports toll rises to 2 dead, 64 wounded in Boston Marathon explosions.
UPDATE 4:45: Attny Gen Holder has directed full resources of Justice Dept to be deployed to Boston investigation (via @Reuters)
UPDATE 4:42: Massachusetts Gov. Deval Patrick has released a statement: "This is a horrific day in Boston. My thoughts and prayers are with those who have been injured. I have been in touch with the President, Mayor Menino and our public safety leaders. Our focus is on making sure that the area around Copley Square is safe and secured. I am asking everyone to stay away from Copley Square and let the first responders do their jobs."
UPDATE 4:36: Boston Police confirm a third explosion at JFK Library (via @Reuters).
UPDATE 4:33: Police getting multiple reports of unexploded devices around Boston (via @BostonGlobe)
UPDATE 4:33: MBTA: police asking people who see anything suspicious to call: 617-222-1212
UPDATE 4:30: Federal law enforcement authority confirmed to ABC News this was an intentional bombing, using small portable explosive devices.
UPDATE 4:28: MBTA: Green Line is terminating service between Kenmore and Park Street Stations and temporarily suspending B- and C-Line service. (via @cbsboston)
UPDATE 4:24: The New York Times has mapped out the two explosions at the Boston Marathon using an aerial photo.
UPDATE 4:21: Intelligence official: 2 more explosive devices found at Boston Marathon; being dismantled. (via @AP)
UPDATE 4:15: FAA issues temporary flight restrictions over area of explosion.
UPDATE 4:08: Boston Police Department confirm there are 2 dead and 22 injured in the explosions.
UPDATE 4:05: USA Today reporting that there are at least three dead and dozens injured.
UPDATE 4:00: Local news reporting a third explosion.
UPDATE: Police have now confirmed that at least one explosion occurred near the finish line of the Boston Marathon at 673 Boylston Street, Reuters reports.
"There was an explosion, police, fire and EMS are on the scene. We have no indication of how many people are injured," a spokeswoman for the Boston Police Department said.
Explosions are being reported near the finish line of the Boston Marathon and authorities are now investigating the matter.
Two loud booms, described as sounding like thunder, were heard around the area of the finish line from inside the Fairmount Copley Plaza Hotel, the Associated Press reports.
As a result, officials closed down the hotel.
The loud booms were heard just moments before.
HERE IS A MAP OF THE LOCATION:
View Boston Marathon Explosion in a larger map