4:29

Jason Gilbert: CBS News reporting that 6 are in critical condition at Mass General hospital alone.
4:30

Jason Sickles, Yahoo News: Cause unknown at this time. No suspects have been identified.
4:30
Boston Police Dept.@Boston_PoliceNews conference in 15 minutes Westin Hotel #tweetfromthebeat via @CherylFiandaca
4:30
NECN@NECN#MBTA police asking people who see anything suspicious to call: 617-222-1212