Throughout the day, we'll be updating with the latest news about the two explosions Monday near the finish line of the Boston Marathon. The blasts killed at least three people -- one of them an 8-year-old boy -- and injured more than 170. We'll also be publishing related posts as the day continues.
Update at 11:35 a.m. ET. Where Things Stand.
DEATHS, INJURIES: Three people were killed and at least 176 were injured, according to Boston Police. At least 17 of the wounded were critically injured.
INVESTIGATION: Authorities searched an apartment in the Boston suburb of Revere late Monday. They left with some bags. There have been no arrests reported and officials aren't commenting on whether anyone is or isn't in custody. A doctor who treated victims says an X-ray indicated that BBs or ball bearings may have been packed into the explosives. Massachusetts Gov. Deval Patrick (D) said that all parcels left at the scene have now been examined and no additional bombs were found.
President Obama told reporters that it's clear this was an "act of terrorism," but that it's not known yet whether it was the act of an individual or a group, and whether it was foreign- or domestic-related.
SECURITY: As Boston and other major cities across the nation and around the world keep their police on alert, there's particular concern in London -- which hosts former Prime Minister Margaret Thatcher's funeral on Wednesday and a major marathon next Sunday. "British officials on Tuesday urged a review of security measures," The New York Times says. Meanwhile, FBI Special Agent in Charge Rick DesLauriers said Tuesday that there are "no known additional threats" in Boston.
Update at 11:35 a.m. ET. This "Act Of Terrorism" Was "Heinous And Cowardly," Obama Says:
Speaking at the White House, the president just said that "given what we now know about what took place, the FBI is investigating it as an act of terrorism." What isn't known, he said, is whether it was the act of an individual or a group, and whether it was foreign- or domestic-related.
The way people at the marathon responded and helped each other, the president added, shows that "the American people refuse to be terrorized" even by such a "heinous and cowardly act."
Update at 11:15 a.m. ET. Obama To Speak:
The White House says President Obama plans to deliver a statement to the nation at 11:30 a.m. ET.
Update at 10:50 a.m. ET. A Heartbreaking Tale.
"Shattered Family: Blast Killed Boy, Wounded Mom & Sister."
Update at 10:10 a.m. ET. 176 Injured; "We Will Go To Ends Of The Earth" To Catch Those Responsible:
At a news briefing now underway, Boston Police Chief Ed Davis just updated the number of people injured. He says there were "176 casualties that presented at hospitals."
FBI Special Agent in Charge Rick DesLauriers then tells reporters that "we will go to the ends of the earth" to apprehend those responsible.
Update at 10:02 a.m. ET. No Comment On Anyone Being In Custody:
Asked if any suspects are in custody, FBI Special Agent in Charge Rick DesLauriers tells reporters he's "not going to say who might or might not be in custody right now."
Update at 10 a.m. ET. "Act Of Cowardice":
The bombings were an "act of cowardice," Suffolk County (Mass.) District Attorney Dan Conley just told reporters. He promised that "justice will be served."
Update at 9:50 a.m. ET. No Known Additional Threats:
There are "no known additional threats," FBI Special Agent in Charge Rick DesLauriers just told reporters in Boston. He also said the investigation will take some time and asked for the public to continue calling in tips and providing photos or videos taken at the scene.
Update at 9:45 a.m. ET. No Additional Bombs Found:
Authorities are now briefing reporters. Massachusetts Gov. Deval Patrick (D) just said that "all ... parcels have been examined" and no additional bombs were discovered at the scene. He said it should be emphasized that "two and only two explosive devices" were involved in the attack.
Update at 9:10 a.m. ET. BBs May Have Been Packed In Bombs:
"Investigators refused to give any specifics on the bombs and say, for example, where they might have been hidden or whether they were packed with shrapnel for maximum carnage, as is often the case in terror bombings overseas," The Associated Press writes. "But Dr. Stephen Epstein of the emergency medicine department at Beth Israel Deaconess Medical Center said he saw an X-ray of one victim's leg that had 'what appears to be small, uniform, round objects throughout it -- similar in the appearance to BBs.' He said it remained to be determined what exactly the objects were."
Update at 8:50 a.m. ET. "Active And Fluid" Investigation:
The Boston Globe writes that "officials last night called the investigation 'very active and fluid.' Authorities were talking to at least one person at Brigham and Women's Hospital, according to sources familiar with the questioning."
Update at 7:45 a.m. ET. On The Young Victim:
"A beloved Dorchester family watching the Boston Marathon near the finish line in Copley Square was caught in one of two bomb blasts that exploded on Monday afternoon," the Dorchester Reporter writes. "Martin Richard, 8, was killed in the explosion, while his sister Jane, 7, suffered a grievous injury to her leg. Their mom, Denise, was also badly hurt in the blast and underwent emergency surgery yesterday to save her life."
Update at 6:50 a.m. ET. More On The Search Of An Apartment In Revere:
As we reported earlier, authorities served a search warrant on a home in the Boston suburb of Revere late Monday, and investigators left with some bags. On its Facebook page, the Revere Fire Department reports that:
"Deputy Chief, Engine 5, Ladder 1, Cataldo Paramedics & Chief were called in for Operational standby for State Police Bomb Techs for search of a 'person of interest' apartment at 364 Ocean Ave. FBI, ATF, ICE, Boston PD, Revere PD as well as MSP detectives and Bomb Techs from Boston PD and State."
Update at 6:40 a.m. ET. Authorities Seeking Photos.
"Good police work," tweets The New York Times' Nicholas Kristof, who is in Boston. "At Boston airport, official is asking every person in security line if they have photos from scene."
6:25 a.m. ET. FBI Takes Charge; Estimate Of Number Injured Rises:
On the morning after explosions ripped through an area packed with runners, spectators, race officials, medical personnel and others at the finish line of the Boston Marathon, the FBI is heading up the investigation into who was responsible.
The Associated Press reports that the FBI "has served a search warrant on a home in suburban Boston in the investigation into the Boston Marathon bombing attack. Massachusetts State Police confirm that a search warrant related to the investigation was served Monday night in Revere, but they haven't said anything else. Some investigators were seen leaving the house early this morning, carrying brown paper bags, plastic trash bags and a duffel bag."
NPR's Dina Temple-Raston reports for Morning Edition that investigators are being very cautious about what they reveal and are cautioning that it may be some time before they can say with any certainty who they think was behind the attack. As she's previously reported, they don't want a repeat of what happened after the bombing at the 1996 Summer Olympics in Atlanta, when security guard Richard Jewell was mistakenly blamed. It took years for investigators to determine that the real bomber was Eric Rudolph, an anti-government, anti-abortion serial bomber.
Along with identifying who was responsible, authorities will also be pushing to determine whether the attacks were foreign- or domestic-related.
The investigation will be aided by the hundreds, if not thousands, of potential witnesses and the large number of videos that were being shot, by professionals and spectators, at the time of the explosions. But the scene is also extremely complicated. Abandoned backpacks and other gear left behind by runners and spectators litter the area. Those have to be searched not only for clues, but for explosives.
As of early Tuesday, authorities said they had not yet taken anyone into custody either as a "person of interest" or a suspect.
Among the other early Tuesday reports:
-- The 8-year-old victim was from nearby Dorchester, Mass., according to the Boston Globe.
-- One person could "easily" have been behind the attacks, retired FBI bomb technician Kevin G. Miles tells the Boston Herald.
-- Boston police plan a 9:30 a.m. ET news conference.
Our colleagues at WBUR have also resumed their live blogging this morning. They report that "overnight the number of injured rose. At last count, at least 151 are being treated at nearly a dozen hospitals around Boston."
As happens when stories such as this are developing, there will likely be reports that turn out to be mistaken. Monday, for example, authorities at one point said they thought there had also been an explosion at the JFK Library in Boston. But it turned out there had been a fire, not an explosion, and there's no known link at this time to the marathon attacks.
We will focus on news being reported by NPR, other news outlets with expertise and statements from authorities in position to know what's going on. And if some of that information turns out to be wrong, we'll update.
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