We’re monitoring the latest news out of Boston. Fox News reports three dead (another report from CNN says 2 fatalities). Video footage of the explosions. Biden reacts. We’ll bring you more as soon as we’re able to confirm new details.

3:50 PM: This probably states the obvious but at moments of high tension it merits repeating. We do not know what happened in Boston. We’ll probably get initial indications soon enough. But it’s highly probable that initials reports will include details end up being inaccurate.

3:59 PM: According to CNN, Boston PD is confirming that two are dead in Boston.

Boston officials will be holding a press conference at 4:30 PM.

WASHINGTON (AP) — Intelligence official: 2 more explosive devices found at Boston Marathon; being dismantled.

The latest we know: At least two news organizations have now published reports appearing to confirm that these were explosive devices. But they are all based on unnamed sources. As yet there is now official government statement to this effect. The AP further reports, with similar sourcing, that two additional explosive devices have been found in the area and are now in the process of being dismantled.

At 4:30 PM, just minutes from now, Boston city officials are scheduled to hold a press conference which may provide additional, official details on what happened. Watch the presser here.

We will update you as we are able to confirm more.

We’ve just confirmed with the Boston Police Department that there was a third explosion this afternoon at the JFK Library in Boston. But there were reportedly no injuries from this incident.

Late Update, 5:07 PM: This incident was discussed at the Boston PD’s 4:30 PM press conference.

Later Update: 5:10 PM: Further updates here.

Boston Police say no arrests, no one in custody, contrary to press report.

Secret Service expands security perimeter around White House.

FBI is no-commenting reports that there is a person or suspect in custody in Boston. This comes after the Boston Police knocked down press reports to that effect.

Obviously there’s a lot of confusion and conflicting accounts at the moment. So we’re going to tell you exactly what we’ve been told by relevant authorities: The Boston Police Department said and still says they know nothing about an arrest. The FBI, however, is declining to comment on the report. Obviously these are not necessarily conflicting reports. It is also possible that federal law enforcement knows things that local law enforcement does not.

5:53 PM: NBC has now confirmed part of the substance of the New York Post account …

Officials say that Boston PD are “guarding” a wounded man at a Boston hospital as a “possible suspect” – @jimmiklaszewski

— NBC News (@NBCNews) April 15, 2013

We’ll let you know more when we hear it.

President Obama will address the country at 6 PM (20 minutes from now), according to Sen. Majority Harry Reid.

5:50 PM: Confirmed by White House.

605 PM: Live video feed here.

One of the two confirmed fatalities in today’s attack is an 8 year old boy.