Federal officials on Thursday unveiled photographs of two people they consider suspects in connection with Monday's bombing at the Boston Marathon and asked the public for help identifying them.
"Somebody out there knows these individuals as friends, neighbors, co-workers or family members," Richard DesLauriers, special agent in charge of the FBI's Boston field office, said during an eight-minute briefing at 5:20 p.m. "Though it may be difficult, the nation is counting on those with information to come forward and provide it to us."
The 11 photos on the FBI's website show two young-looking men – "Suspect One" wearing a dark hat, "Suspect Two" wearing a white hat. They appear to be associated. They strolled through the marathon crowds near the finish line, and Suspect Two sets down a backpack at the site of the second of two explosions, DesLauriers said.
He said the only photos that should be relied on were the ones the FBI released Thursday at its news briefing at the Sheraton Boston Hotel and on the bureau's website, fbi.gov.
More than 1,000 federal, state and local law enforcement officials have taken part in the massive investigation and manhunt. The FBI Boston's Joint Terrorism Task Force is coordinating the 30 federal, state and local law enforcement agencies.
Together, they have combed through more than 3,000 images. Asked about whether the suspects had gone through the FBI's facial recognition system, FBI Supervisory Special Agent Jason Pack said the government was using "every available technology the government has."
"It's a long, tedious process, but they're doing it as fast as they can," he said.
Even so, DesLauriers stressed that the task force needed the public's help.
"No bit of information, no matter how small or seemingly inconsequential, is too small for us to see," he said. "Each piece moves us forward toward justice."
He added, "As I said two days ago, we are working methodically and with a sense of urgency to identify those responsible for the bombings."
Investigators continued working Thursday, picking through videotape and explosive fragments with an expertise honed on foreign wars and terrorist attacks, and sifting through thousands of tips.
The briefing came after a back-and-forth day Wednesday when some media outlets wrongly reported that there had been an arrest in the bombings, and were forced to retract those reports. A scheduled briefing for Wednesday afternoon never materialized.
Thursday's press conference took place in a crowded hotel ballroom not far from the site of the bombings in Boston's Copley Square.
The briefing came several hours after President Barack Obama attended an interfaith service in Boston for the bombing victims and then visited many of them in the hospitals where they're being treated.
The two bombs went off in short succession around 2:50 p.m. Monday near the finish line of the Boston Marathon. The blasts killed three people, including 8-year-old Martin Richard, and wounded nearly 200. Physicians have performed multiple amputations on victims, whose ages range from as young as 2 to as old as 78.
The dual blasts sent fragments of glass, plastic, metal and other materials rocketing into victims' bodies, physicians said, with some evidence that the shrapnel included nails and BB-like pellets that might have been deliberately placed inside the weapons to boost their lethality.
At Brigham and Women's Hospital, officials said Thursday afternoon that they'd treated a total of 35 patients related to Monday's explosions. Ten patients remain in the hospital, with three listed in critical condition.
There was good news on the recovery front. Boston Children's Hospital sent an injured 3-year-old home to his family. The Woolfenden family, who withheld the boy's first name, released a statement thanking emergency responders, volunteers and runners "who selflessly rushed in to help" after the explosion.
By Lesley Clark and Chris Adams
McClatchy Newspapers