An official briefed on the Boston Marathon terror bombing investigation said today that authorities have an image of a suspect carrying, and perhaps dropping, a black bag at the second bombing scene on Boylston Street, outside of the Forum restaurant.

Investigators are “very close’’ in the investigation, said the official, who declined to be named.

The Globe’s source also said a surveillance camera at Lord & Taylor, located directly across the street, had provided clear video of the area, though it was unclear whether the image of the suspect was taken from that camera.

“The camera from Lord & Taylor is the best source of video so far,’’ confirmed Dot Joyce, a spokeswoman for Boston Mayor Thomas M. Menino. “All I know is that they are making progress.’’


Few other details were released by officials today about the progress of the investigation. Officials scheduled, rescheduled and eventually canceled an FBI briefing intended to update the public. No time was given for the next briefing.

Two bombs exploded within seconds of each other at 2:50 p.m. Monday near the Boylston Street finish line of the world-renowned race, killing three people and injuring 176, many of whom suffered major trauma from flying shrapnel, including nails and ball bearings that authorities have said were stuffed into the explosive devices by their makers.

A massive investigation is underway, involving local, state, and federal law enforcement. Officials have promised to go to the “ends of the earth’’ to find whoever is responsible.

Authorities had appealed to the public for video and photographs of the area near the bombing scene at the finish line of the marathon, noting that many people among the crowd were likely to have taken photos of the conclusion of the event, where runners are cheered on by admiring crowds. The authorities vowed to study the myriad images “frame by frame.’’

A spokesman for President Obama said at a Washington media briefing that the president would bring a message of “resolve’’ and “commonality’’ when he travels to the city Thursday for an interfaith service at the Cathedral of the Holy Cross.


“The way that the people of Boston and the city of Boston responded reminds us — and reminds the world — of just who we are as a people,’’ Jay Carney said in a media briefing in Washington, where he was also questioned about poisoned letters sent to the president and a senator.

Asked whether the letters and the bombs were considered linked, Carney deferred to an FBI statement that said there was no indication of a connection.

The bombings killed Martin Richard, 8, of Dorchester; Krystle Campbell, 29, of Arlington, and Boston University graduate student Lingzi Lu, a native of Shenyang, China, who was in her 20s.

The Globe reported today that investigators had found evidence that timing devices were used to detonate the bombs. Working at the city’s largest-ever crime scene, investigators also determined that bombs were probably fashioned from 6-liter pressure cookers, filled with nails and small ball bearings, like buckshot, to increase the carnage, and then hidden in black nylon bags or backpacks and left on the ground.

CNN and the Associated Press reported this morning that the lid of one of the pressure cookers was located on the rooftop of a nearby building.

Pressure cooker company Fagor America Inc. said in a statement this afternoon that it had been “contacted by government investigators and are extending our full cooperation.’’

FBI bomb experts at the FBI Academy in Quantico, Va., will try to rebuild the devices from fragments that include a circuit board that indicated the bombs were detonated on a timer, rather than remote control.


The FBI, which is leading the investigation into the bombing, had asked the public for tips on anyone who may have been lugging a heavy black bag near the finish line.

Confusion reigned for about an hour this afternoon as news organizations reported, based on sources, that a suspect was in custody or under arrest, reports that were soon contradicted by official statements from law enforcement.

The Associated Press first reported at about 2 p.m. that a suspect had been “taken into custody’’ and was “expected in federal court’’ on the South Boston waterfront. AP did not name the source of the information. CNN followed with a tweet saying “arrest made’’ in the case.

The Globe, relying on information provided by an official familiar with the investigation, also sent out tweets and posted a story reporting that a suspect was in custody and en route to federal court.

The FBI later issued a statement saying “no arrest has been made;’’ other public officials also said no one was in custody. After further reporting, the Globe is no longer convinced that its previously reliable source had accurate information.

Amid the crosscurrents of conflicting information, spectators, photographers, and reporters flocked to the federal courthouse on the South Boston waterfront, expecting the suspect to be brought there for a court appearance. People were evacuated after a bomb threat was received. The building was later declared to be safe.