One of the dead was an 8-year-old boy, according to a state law enforcement source.
Hospitals reported at least 144 people are being treated, with at least 17 of them in critical condition and 25 in serious condition. At least eight of the patients are children.
At least 10 people injured had limbs amputated, according to a terrorism expert briefed on the investigation.
Several of the patients treated at Massachusetts General Hospital suffered injuries to lower limbs that will require “serial operations” in the coming days, trauma surgeon Peter Fagenholz said Monday night. Some injuries were so severe amputations were necessary, Fagenholz added.
[Update, 11:41 p.m. ET] Stephen Segatore, a nurse who was at the medical tent near the finish line for the Boston Marathon, said emergency responders immediately went into mass-casualty mode.
“We had full trauma response at the scene,” he told CNN. “We had physicians, nurses who are experienced in trauma care. We had EMTs and it was a full Level 1 trauma experience.”
Segatore said he treated at least 25 people as those experienced in trauma care stepped forward while others treated people with minor injuries.
[Update, 11:35 p.m. ET] Saudi ambassador to the United States Adel bin Ahmed Al-Jubeir condemned the bombings in Boston and offered his condolences to victims’ families.
“What occurred today in Boston is a heinous crime which contradicts the values of humanity.” he said.
[Update, 10:52 p.m. ET] The total of injured has risen to 144 people, officials at Boston area hospitals said. That includes three additional patients at Brigham and Women’s Hospital.
[Update, 10:41 p.m. ET] A law enforcement source in Boston tells CNN that investigators have a “number of active leads, and some good early progress in the forensics analysis.”
[Update, 10:07 p.m. ET] Dr. Peter Fagenholz told reporters that there were 29 wounded people at Massachusetts General Hospital, eight of whom were in critical condition. Many of the people had shrapnel injuries to their lower extremites, he said.
“We have performed several amputations,” he said.
There were no pediatric patients among the wounded, he said.
[Update, 9:38 p.m. ET] Dr. Allan Panter, who was near the finish line waiting for his wife who was running the race, told CNN he was standing about 20 to 25 feet from the first blast. He said he treated victims on the street after the explosion.
“I saw at least six to seven people down next to me,” he said. “They protected me from the blast. One lady expired. One gentleman lost both his (lower) limbs. Most of the injuries were lower extremities. I could not figure out why the young lady had expired. I could not find any injury on her thorax.”
[Update, 9:28 p.m. ET] Bill Iffrig, seen in video wearing an orange tank top and being blown over as he approached the finish line, told CNN’s Piers Morgan that he was feeling OK after the blast.
“I got down to within about 15 feet of the finishing apron and heard just tremendous explosion, sounded like a bomb went off right next to me, and the shock waves just hit my whole body and my legs just started jittering around,” he said. “I knew i was going down and so i ended up down on the blacktop.”
Iffrig, 78, said he was assisted by one of the event volunteers, who helped him up so he could finish the race. After that, the worker looked for aid for Iffrig, who had just a scratch from his fall.
“He insisted on getting a wheelchair over there so we started to do that, but then before that was rounded up, i said my hotel’s about six blocks away so I think I can make it okay. So they let me get out of there and I went on home to my wife.”
[Update, 8:55 p.m. ET] A Saudi national with a leg wound was under guard at a Boston hospital in connection with the bombings at the Boston Marathon, but investigators cannot say he is involved at this time and he is not in custody, a law enforcement official said Monday evening.
[Update, 8:54 p.m. ET] Three people were killed in the bombings, Boston Police Commissioner Ed Davis told reporters Monday night, raising the toll by one.
[Update, 8:52 p.m. ET] The FBI is taking the lead in the investigation, Rick DesLauriers, FBI Special Agent in Charge of the Boston field office, told reporters.
[Update, 8:44 p.m.ET ] The Boston Celtics home game against the Indiana Pacers, originally scheduled for Tuesday, was canceled, the NBA announced. With the regular season almost at its end, the contest will not be made up.
[Update, 8:36 p.m. ET] Investigators have warned law enforcement officers to be on the lookout for a “darker-skinned or black male” with a possible foreign accent in connection with Monday’s bombings at the Boston Marathon, according to a law enforcement advisory obtained by CNN.
The man was seen with a black backpack and sweatshirt and was trying to get into a restricted area about five minutes before the first explosion, the lookout notice states.
[Update, 8:35 p.m.] Hospital workers have treated 141 people after the Boston Marathon bombings, officials at those facilities said Monday night. Two people died in the terror attack, including an 8-year-old boy, a state law enforcement source said.