UPDATE (2:21 p.m./ET): "Every one of us stands with you," President Obama said at an interfaith service inside the Cathedral of the Holy Cross in Boston earlier today. Turning his attention to the perpetrator(s) of the "heinous and cowardly act" of bombing the Boston Marathong, the president said: ""Yes, we will find you. And yes, you will face justice. We will hold you accountable."
Meanwhile, the FBI-led investigation continues to push forward, with two men rerportedly being the prime targets of the search for those responsible for the attack in Boston Monday.
A Boston Red Sox hat is seen among a makeshift memorial for the victims of the Boston Marathon bombings on Boylston street in Boston, Massachusetts April 18, 2013.
UPDATE (4/18, 7:13 a.m./ET): Info continues to trickle in as a massive FBI-led investigation continues to search for the person or person responsible for the bombing in Boston on Monday afternoon at the Boston Marathon. Two men seen in images near the finish line of the race, moments before two bombs there exploded, are of "high interest" and are considered "possible suspects," a law enforcement official said. As of Wednesday evening, Boston-area hospitals had released at least 112 of the 178 people treated for injuries sustained in Monday's attack near the Boston Marathon's finish line, according to a CNN tally. Thirteen of those still hospitalized remain in critical condition, hospital officials said. As of Wednesday evening, Boston-area hospitals had released at least 112 of the 178 people treated for injuries sustained in Monday's attack near the Boston Marathon's finish line, according to a CNN tally. Boston and D.C. remain on high alert. President Barack Obama and first lady, Michelle, are scheduled to attend an interfaith service for the victims in Boston this morning.
UPDATE (2:45 p.m./ET): CNN is backtracking on their report about a suspect being arrested; Department of Justice officials say no arrest has been made.
UPDATE (2:26 p.m./ET): CNN is reporting that a suspect has been arrested. According to an official source, two videos led to the arrest. A briefing is expected at 5 p.m./ET.
UPDATE (1:21 p.m./ET): Reports indicate Boston police have identified a suspect in the bombings. A briefing is expected at 5 p.m./ET. Meanwhile, letters sent to President Obama and Senator Roger Wicker (R-Mississippi) testing positive for deadly poison ricin were intrecepted and are being further tested and investigated. Boston and now D.C. are on elevated alert.
UPDATE (April 17, 7:15 a.m./ET): A candlelight vigil was held for the victims of Monday's terrorist attack on Boston last night; a huge crowd turned out to show support for the three dead, 183 injured from the bombings that were carried out near the finish line of the Boston Marathon. Boston remains locked down as authorities undertake a massive investigation to learn what exactly happened and who carried out the "heinous and cowardly" attack. Authorities are processing "the most complex crime scene that we have dealt with in the history of our department," said Ed Davis, the Boston police commissioner. CNN has a special "What We Know" page; click here.
UPDATE (1:30 p.m./ET): In a televised address to the nation, President Obama described yesterday's terrorist attack on Boston as a "heinous and cowardly act." A massive investigation, led by the FBI and involving Homeland Security is underway in Boston after two bombs were detonated near the finish line of the Boston Marathon. The number of injured as a result of the blasts is now put at more than 170, with three dead.
As CNN notes, "The blasts marked a grotesque end to what should have been a celebration of triumph."
UPDATE (11:20 a.m./ET): President Obama is set to speak at 11:30 a.m./ET after being advised by top administration officials, including from Homeland Security. CNN reports that investigators are combing through what Boston's top police official described as "the most complex crime scene we've dealt with in the history of our department." "Boston will overcome," Mayor Thomas Menino promised.
UPDATE (April 16, 5:30 a.m./ET): Three people, including an eight-year-old boy, are dead as a result of twin blasts detonated near the finish line of the Boston Marathon yesterday afternoon, Boston police say. Area hospitals say at least 144 are injured, including eight children, with many in critical condition. According to CNN, at least 17 people are reported to still be in critical condition. "The full horror of Monday's bomb attacks in Boston was reflected in emergency rooms across the city as doctors were forced to perform amputations and treat injuries normally expected on a battlefield.">
But Rep. Bill Keating, D-Massachusetts, said two undetonated devices were found. One was discovered at a hotel on Boylston Street near the bomb site, and another was found at an undisclosed location, said Keating, a member of the House Homeland Security Committee. He called the bombing a "sophisticated, coordinated, planned attack."
The FBI is now in charge of the investigation; they do consider this a terrorist attack.
UPDATE (8:07 p.m./ET): CNN is now reporting that at least two are dead, including an 8-year-old boy, and more than 130 are injured as a result of two bomb lasts this afternoon at approximately 2:50 p.m./ET, near the finish line of the Boston Marathon. At least 17 of the injured are in critical condition in Boston area hospitals.
U.S. Rep. Bill Keating, D-Massachusetts, said an unexploded device was found at a hotel on Boylston Street, and another unexploded device was found at an undisclosed location.
Keating, who is a member of the House Homeland Security committee and has spoken to law enforcement sources, told CNN's Dierdre Walsh that the incidents were a "sophisticated, coordinated, planned attack."
Doctors are "pulling ball bearings out of people in the emergency room," a terrorism expert briefed on the investigation told CNN's Deborah Feyerick.
The U.S. Department of Homeland Security, other federal security agencies, as well as both state and local authorities are investigating and monitoring the situation. In his address at 6:20 p.m./ET, President Obama said he has "directed the full resources of the federal government to help state and local authorities protect our people, increase security around the United States as necessary, and investigate what happened."
CNN continues to update regularly on their This Just In blog.
DAN LAMPARIELLO / DOBSONAGENCY / REX USA
UPDATE (6:20 p.m./ET): President Obama has spoken to the nation on the terrorist attack in in Boston: "All Americans stand with the people of Boston ... We still do not know who did this or why ... but make no mistake: We will get to the bottom of [this]. We will find out who did this. We will find out why they did this. ... Any responsible groups will feel the full weight of justice ... The American people will say a prayer for Boston tonight, and Michelle and I send out deepest thoughts and prayers to the victims."
There is still a great deal of uncertainty in the aftermath of two bomb blasts this afternoon exploding near the finish line of the Boston Marathon. At least two are dead, dozens are injured, many critically. The explosions occurred at about 2:50 p.m., more than two hours after the first of the race's nearly 27,000 runners had crossed the finish line.
Click here for CNN.com's This Just In blog for the latest.
UPDATE (5:50 p.m./ET): Officials are saying the JFK Libray incident was "fire related," not an explosion or related to the two blasts at the marathon's finish line. The Boston Globe is reporting that there were at least 100 injuries stemming from the explosions at the marathon finish line. The New York Post is reporting that authorities have a suspect--a Saudi national--who is under guard at a Boston hospital. President Obama will address the nation about the events in Boston at 6:10 p.m./ET.
UPDATE (5:18 p.m./ET): Two bombs exploded at the finish line of the Boston Marathon, another blast struck the JFK Presidential Library, which the Boston police believe is related. Two have died and hospitals are reporting as many as 51 injured, with numerous in critical condition. The City of Boston is begining a press conference now.
It was unclear who may have planted the bombs. There were no credible threats before the race, a state government official said. Authorities in Boston found at least one other explosive device that they were dismantling.
For families of victims and for those trying to reunite with family members and runners, phone 617-635-4500.
Live updates at CNN.com.
UPDATE (4:40 p.m./ET): Blasts near the finish line of the Boston Marathon killed two people and injured 28others Monday afternoon, Boston police said. At least six of the injured are in critical condition.
"We are currently in contact with federal, state and city officials," Massachusetts Gov. Deval Patrick wrote on Twitter.
The explosions occurred at about 2:45 p.m., more than two hours after the first of the race's nearly 27,000 runners had crossed the finish line, CNN Producer Matt Frucci reported.
The race was halted as was subway service into the area.
An official has told CNN that Boston Firefighters found what they think is an unexploded device after blasts that killed 2 people at Boston Marathon.
Photo of an explosion at the Boston Marathon finish line.
UPDATE (4:10 p.m./ET): Boston police are reporting that two are dead, at least 22 injured as a result of two explosions near the finish line of the Boston Marathon this afternoon.
Video is beginning to hit the Web, including this one:
Two explosions at the finish line of the Boston Marathon have resulted in injuries, The Associated Press is reporting.
Boston Globe News tweeted: "BREAKING NEWS: Two powerful explosions detonated in quick succession right next to the Boston Marathon finsh line this afternoon."
Bloody spectators were being carried this afternoon 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.
"There are a lot of people down," one man, whose bib No. 17528 identified him as Frank Deruyter of North Carolina, told the AP. He was not injured, but marathon workers were carrying one woman, who did not appear to be a runner, to the medical area as blood gushed from her leg. A Boston police officer was wheeled from the course with a leg injury that was bleeding.
About three hours after the winners crossed the line, there was a loud explosion on the north side of Boylston Street, just before the photo bridge that marks the finish line. Another explosion could be heard a few seconds later.
NBC News has more here.
For live updates via the New York Times, click here.
Photo of scene near finish line of Boston Marathon, photo by Twitter user Tyler Wakstein at theoriginalwak.