Boston Marathon Bombings Update: Person of interest held, apartment searched in connection to explosions, report says

(CBS/AP) BOSTON - Law enforcement officers investigating the Boston Marathon bombings searched a suburban apartment in Revere, Mass. on late Monday belonging to a man being questioned in connection with the attack, CBS Boston reports.

PICTURES: Explosions near Boston Marathon finish line

CBS News senior correspondent John Miller reported Tuesday morning that the man is a Saudi national and is being held under guard at an area hospital. He was reportedly seen running from the explosion, and a civilian chased him down and tackled him. 

The man was turned over to Boston police and was being interviewed by the FBI. He was being cooperative and denied any involvement, CBS News reports.

Massachusetts State Police confirmed to The Associated Press that a search warrant related to the probe was served Monday night in Revere, but provided no further details. Some investigators were seen leaving the apartment building early Tuesday carrying brown paper bags, plastic trash bags and a duffel bag.

The search lasted nine hours and several bags were removed from the scene around 2 a.m. Tuesday but authorities would not comment on the search, CBS Boston reports. The Revere Fire Department wrote on its Facebook page that the search pertained to "a person of interest."

Miller said the man was being treated for burns on his hands, and authorities suggest he may be in the U.S. on a student visa.

Two bombs exploded in the crowded streets near the marathon finish line, killing at least three people and injuring more than 140 in a bloody scene of shattered glass and severed limbs that raised alarms that terrorists might have struck again in the U.S.

One of the dead was an 8-year-old boy identified by the Boston Globe as Martin Richard. His mother and sister were also injured in the blasts while they were waiting for his father to finish the race.

Federal investigators said no one claimed responsibility for the bombings and there's no word yet on a motive. But a White House official speaking on condition of anonymity said Monday's attack was being treated as an act of terrorism.

Hospitals reported at least 144 injured, at least 17 of them critically. The injuries ranged from cuts and bruises to amputations. Many victims suffered lower leg injuries and shrapnel wounds. Some suffered ruptured eardrums.

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