Two unexploded devices were discovered by police near the site of the Boston Marathon's finish line, reports the Associated Press:

BREAKING: Intelligence official: 2 more explosive devices found at Boston Marathon; being dismantled — The Associated Press (@AP) April 15, 2013

That seems to be in addition to the two bombs that exploded and a third that was part of a controlled explosion by police officers. NBC reports that the devices are believed to be homemade.

BREAKING: Small homemade bomb is preliminary cause of explosion at Boston Marathon, law enforcement officials tell NBC News — NBC Nightly News (@nbcnightlynews) April 15, 2013

The New York Times mapped out where exactly the initial explosions took place. There was an additional fire at the JFK Library, but an official there confirmed it was unrelated to the explosions at the marathon.

We'll stay updated with more news about the situation as it comes in.