2013 Boston Marathon finish line

At least three people were killed and more than 130 people were injured by two large explosions near the finish line of the Boston Marathon Monday, according to news reports.

Law enforcement officials confirmed that one of the fatalities was an 8-year-old boy, and at least eight more children were among the injured.

Several eyewitnesses told The Boston Globe that they saw people who had lost their limbs. "It was just an explosion, it came out of nowhere," Boston.com producer Steve Silva, who was at the scene covering the race said. "There are multiple injuries. I saw dismemberment, I saw blood everywhere. People are badly injured."

The explosions happened at about 2:45 p.m. ET, about an hour after the first runners had crossed the finish line, according to reports. The 26th mile of the race was dedicated to the victims of the shooting at Sandy Hook Elementary School last year.

In a news conference late Monday, President Barack Obama called the explosions a "senseless loss" and said that the prayers of the American people were with those in the "tough and resilient" city of Boston.The President acknowledged that the investigation is ongoing, and said that Boston has "every single federal resource necessary" as the city continues to deal with the aftermath of Monday's events. "We still do not know who did this or why, and people should not jump to conclusions," the President said. "But make no mistake. We will get to the bottom of this. We will find out who did this and why they did this." He also promised that those responsible "will feel the full weight of justice."

According to CNN, a Saudi national with a leg wound was under guard at a Boston hospital in connection with the bombings as of late Monday evening, but investigators have not commented on specifics of the investigation, including suspects and possible leads. Earlier in the evening, investigators also reportedly sent a law enforcement advisory warning authorities to be on the lookout for a "darker-skinned or black male" with a possible foreign accent in connection with the bombings. The man was seen with a black backpack and sweatshirt and had been trying to get into a restricted area about five minutes before the first explosion.

Contrary to earlier reports about a third explosion at the nearby JFK Library, the explosion was later discovered to be an accidental fire that occurred in the mechanical room at the library and was not linked to the other two explosions. A spokesperson for the library told CBS that there were no reported injuries. However, Boston Police Commissioner Edward Davis did confirm that a third explosive device was found on Boylston Street — the same street where the first two explosions took place — but it was detonated via a controlled explosion by authorities.

When asked if officials believed Monday's events to be a terrorist attack, Davis was guarded. "We're not being definitive on this right now, but you can reach your own conclusions based upon what happened," he said. David, and Massachusetts Governor Deval Patrick, who also spoke at Monday's news conference, could not give an updated number of those killed and those injured from the explosions.

Portions of the subway in Boston have been shut down and police are encouraging spectators to evacuate the area. The Federal Aviation Administration (FAA) has grounded all flights that were to set to take off from, or land at, Boston's Logan International Airport on Monday. Security has also been stepped up in Washington, D.C. and New York City, according to news reports.