(CBS/AP) - The Boston Police Department says that at least two people were killed and 23 injured in two explosions near the finish line of the Boston Marathon.
The White House said President Barack Obama has been notified about the explosions. The administration said it is in contact with state and local authorities and the president directed his administration to provide whatever assistance is necessary in the investigation and response.
Vice President Joe Biden was on a conference call with gun control activists when staffers turned on televisions in his office Monday to view coverage of the explosions. Biden said during the call that his prayers were with those who suffered injuries.
About three hours after the winners crossed the finish line, there was a loud explosion on the north side of Boylston Street, just before the photo bridge that marks the finish line. Another explosion could be heard a few seconds later.
Smoke rose from the blasts, fluttering through the national flags lining the route of the world's oldest and most prestigious marathon. TV helicopter footage showed blood staining the pavement in the popular shopping and tourist area known as the Back Bay.
"There are people who are really, really bloody," said Laura McLean, a runner from Toronto, who was in the medical tent being treated for dehydration when she was pulled out to make room for victims of the explosions. "They were pulling them into the medical tent."
Runners who had not finished the race were diverted straight down Commonwealth Avenue and into a family meeting area, according to an emergency plan that had been in place.
The nearby Prudential Tower, the city's second-tallest building with an upscale shopping mall on the ground, was evacuated, along with the luxury Mandarin Oriental hotel, according to media reports.
All off-duty police officers have been called in to assist, according to an order given over a police scanner. Armored vehicles and police dogs were also asked to head to the scene.
Race day got started with 26 seconds of silence in honor of the victims of the December school shooting in Connecticut. A little more than 2 hours later, the lead runners passed the Mile 26 marker, which was decorated with the Newtown, Connecticut, seal and dedicated to the memory of those killed there.
The annual 26.2-mile (42-kilometer) marathon takes place on Patriot's Day, a state holiday that celebrates the evacuation of Boston by the British in the American Revolution.