Update at 2:37 p.m.: Boston Police tweets:
Despite reports to the contrary there has not been an arrest in the Marathon attack.— Boston Police Dept. (@Boston_Police) April 17, 2013
Update at 2:28 p.m.: NPR News reports no arrests yet.
Update at 2:22 p.m.: WBUR's David Boeri is in Boston federal court and is awaiting developments there. Listen to WBUR-FM special coverage here.
Update at 2:12 p.m.: It's worth noting that while several outlets, including the AP, are saying an arrest has been made, other outlets, including NBC andCBS, are not confirming an arrest has been made.
Update at 2:05 p.m.: The Associated Press says the suspect is now in custody.
Update at 1:58 p.m.: The AP has a full story now: "Official: Arrest Imminent In Marathon Bombing"
There will be a briefing at 5PM this evening...stay tuned!