Two explosions disrupted the Boston Marathon on Monday, causing injuries and scattering crowds near the finish line, witnesses said.

The blasts occurred after the top racers had completed the course, but thousands of others were still running. CNN reported that authorities halted the race.

Video footage showed smoke rising from a sidewalk and people running away.

A CNN producer who was at the race said the first large explosion was followed about 10 seconds later by another blast. He said he saw at least five or six people who appeared to be injured.

Emergency personnel rushed to the area, and the street was quickly sealed off.