[00:36.03]One runner collapsed apparently struck by an object seconds later as terrified onlookers tried to get away.
[00:42.63]Picture showed another plume of smoke rising from the second blast down the road.
[00:46.74]Emergency workers immediately began tearing at the pavement barriers and flag poles to get the wounded behind.
[00:53.08]There were clearly many injured people.
[00:55.34]Injured spectators were carried to the nearby medical tents set up to look after exhausted runners.
[01:00.88]Some news just in. Boston police said the explosions at the finishing line of the city's marathon were almost simultaneous.
[01:07.31]They say no further explosive devices have been found so far near the finish line, but the investigation is ongoing.
[01:13.48]The Boston police commissioner Edward Davis told the news conference that there had been a third explosion.
[01:18.69]"We have, at this point of time, determined that there has been a third incident that has occurred.
[01:26.74]There was an explosion that occurred at the JFK library.
[01:31.11]So this is very much an ongoing event of this point time.
[01:34.40]We are not certain that these incidents are related, but we are treating them as if they are."
[01:39.56]Police in Boston have urged the residents of the city to stay indoors and not to congregate in large groups.