A suspect in the deadly Boston Marathon bombings was taken into custody in a breakthrough that came less than 48 hours after the attack, a law enforcement official briefed on the investigation said Wednesday.

The official spoke shortly after several media outlets reported that a suspect had been identified from surveillance video taken at a Lord & Taylor department store between the sites of the blasts, which killed three and wounded more than 170. The dead included a child, a young woman and a female student from China.

The official was not authorized to divulge details of the investigation and spoke to The Associated Press on condition of anonymity. The suspect was expected at a Boston courthouse, the official said.

A news briefing was scheduled later Wednesday.

President Barack Obama called the attack on the world's most famous marathon an act of terrorism. Obama planned to attend an interfaith service Thursday in the victims' honor in Boston.

Law enforcement agencies had pleaded for the public to come forward with photos, videos or any information that might help them solve Monday's twin bombings near the race's finish line. The bombs exploded 10 or more seconds apart just next to the race course, tearing off victims' limbs and spattering streets with blood. The blasts went off minutes after the four-hour mark of the race.

The bombs involved kitchen pressure cookers packed with explosives, nails and other lethal shrapnel. But the FBI said nobody had claimed responsibility.

An intelligence bulletin issued to law enforcement includes a picture of a mangled pressure cooker and a torn black bag that the FBI said were part of a bomb that exploded during the marathon.

Authorities have recovered a piece of circuit board that they believe was part of one of the explosive devices, and they found the lid of a pressure cooker that apparently was catapulted onto the roof of a nearby building, a law enforcement official said Wednesday. The official spoke on condition of anonymity because this person was not authorized to publicly discuss evidence in the ongoing investigation.

The blasts killed 8-year-old Martin Richard and 29-year-old Krystle Campbell. The Shenyang Evening News, a state-run Chinese newspaper, identified the third victim as Lu Lingzi. She was a graduate student at Boston University.

Scores of victims remained in hospitals, many with grievous injuries. A 5-year-old child, a 9-year-old girl and 10-year-old boy were among 17 victims listed in critical condition.

The trauma surgery chief at Boston Medical Center says most of the injuries his hospital treated were to the legs.

"We have a lot of lower extremity injuries, so I think the damage was low to the ground and wasn't up," Dr. Peter Burke said. "The patients who do have head injuries were blown into things or were hit by fragments that went up."

At Massachusetts General Hospital, all four amputations performed there were above the knee, with no hope of saving more of the legs, said Dr. George Velmahos, chief of trauma surgery.

"It wasn't a hard decision to make," he said Tuesday. "We just completed the ugly job that the bomb did."

Pressure-cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 intelligence report by the FBI and the Homeland Security Department. One of the three devices used in the May 2010 Times Square attempted bombing in New York City was a pressure cooker, the report said.

"Placed carefully, such devices provide little or no indication of an impending attack," the report said.

But information on how to make the bombs is readily found online, and U.S. officials said Americans should not rush to judgment in linking the attack to overseas terrorists.

___

Associated Press writers Eileen Sullivan in Washington; Jay Lindsay, Pat Eaton-Robb, Steve LeBlanc, Bridget Murphy, Rodrique Ngowi and Meghan Barr in Boston; Julie Pace and Lara Jakes in Washington; Paisley Dodds in London; Lee Keath in Cairo; and Marilynn Marchione in Milwaukee contributed to this report along with investigative researcher Randy Herschaft in New York.