Horrific:

Two explosions at the finish line of the Boston Marathon have resulted in injuries.

Bloody spectators were being carried Monday to the medical tent that had been set up to care for fatigued runners. Police wove through competitors as they ran back toward the course.

The most frightening Tweet thus far, from local reporter Jackie Bruno:

I saw people’s legs blown off. Horrific. Two explosions. Runners were coming in and saw unspeakable horror.

CNN reports that the area is being treated as a “crime scene.”

Folks, please be very careful about what you tweet or retweet on this.

I’ll be updating here.

Update: The Boston Globe estimates that “at least dozens” have been “seriously injured.”

Update: On CNN, Wolf Blitzer — appropriately — keeps urging caution about jumping to conclusions about the cause of the explosions. No official word from law enforcement yet.

Update: Multiple reports are noting the timing of the explosions: They seem to have occurred around the halfway mark of people crossing the finish line; many had already crossed, but thousands more were following.

Update: So awful, from an ABC affiliate:

MGH trauma nurse says people coming in with severed limbs, kids with severe burns & many casualties

MGH is Massachusetts General Hospital.

Update: Boston police have told CNN that two are dead, and 22 are wounded. That’s the most up to date casualty count I’ve heard.

Update: CNN’s Peter Hamby talks to an eyewitness who claimed, as Hamby put it, that the first explosion “felt like a huge cannon,” while the “second explosion” came out of what the witness “said was a trash can.”

Update: The Associated Press quotes an “intelligence official” claiming that there have been two more explosive devices found at the Boston Marathon; they’re being dismantled.

Update: According to HuffPo’s Sam Stein, CBS News quoted a law enforcement official claiming they have a surveillance photo of a potential suspect.

Update: The New York Times reports:

[A] senior United States government official said that the Boston police and the F.B.I. said they had received no reports in recent days about a threat of an attack on the marathon and that there was no warning on Monday.

Also, be sure to follow breaking news on our Early Lead liveblog.

Update: I can’t vouch for the accuracy of this tweet, from the NBC Sports Network, but I’m posting it in hopes that it is true, and if so, for what it says about the better side of human nature in situations such as these:

Reports of Marathon Runners that crossed finish line and continued to run to Mass General Hospital to give blood to victims

Update: The Boston Police Commissioner says there has been a third explosion, at the JFK Library; police aren’t certain they are related to the others but are assuming that it was. The commissioner adds that there were injuries relating to the third explosion.

Update: The latest injury count, from the Boston Globe:

Boston hospitals report more than 100 being treated after Marathon explosions.

Still two dead, according to most outlets.

Update: The Boston police claim the incident at the JFK Library “appears to be fire related.”

Update: The White House posts a photo of President Obama being briefed on the bombings by FBI director Robert Mueller.

Update: The JFK Library Tweets:

All staff and visitors are safe and accounted for. Thank you.

Update: Video of one of the main explosions is right here.

Update: CNN just reported that the FBI is now characterizing the bombings as a terrorist attack; the FBI does not know whether it is foreign or domestic.

Update: President Obama, in a statement to reporters just now:

Earlier today I was briefed by my Homeland Security team on the events in Boston. We’re continuing to monitor and respond to the situation as it unfolds. And I’ve directed the full resources of the federal government to help state and local authorities protect our people…The American people will say a prayer for Boston tonight. And Michelle and I send our deepest thoughts, prayers to the families of the victims in the wake of this senseless loss.

We don’t yet have all the answers. But we do know that multiple people have been wounded, some gravely, in explosions at the Boston Marathon. I’ve spoken to FBI director Mueller, and Secretary of Homeland Security Napolitano, and they’re mobilizing the appropriate resources to investigate and to respond. I’ve updated leaders of Congress in both parties, and we reaffirmed that on days like this, there are no Republicans or Democrats; we are Americans, united in concern for our fellow citizens. [...]

We still do not know who did this, or why. And people shouldn’t jump to conclusions before we have all the facts. But make no mistake: We will get to the bottom of this. And we will find out who did this. We’ll find out why they did this. Any responsible individuals — any responsible groups — will feel the full weight of justice.

 

RELATED: Images from the Boston Marathon explosions

 

 

 

 

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.