BOSTON — Federal investigators said Thursday they have clear video images of two male suspects in the Boston Marathon bombings that killed three and injured 175 but they have not been able to find or identify the individuals.
Circulation of the images has been limited so far to law enforcement officials to avoid tipping off the suspects, but the video frames could be released to the public soon in an expanded effort to put names to the faces.
Officials said the individuals were considered suspects because they are seen carrying black bags at the two bomb sites 100 yards apart near the marathon's finish line area. Black remnants of duffel bags or backpacks were found by forensic experts at those same sites.
The suspects images came from the frame-by-frame scrutiny of scores of videos collected from spectators, television stations, race organizers and business security cameras of the crime scene before and after the bombings at 2:50 p.m. Monday.
In Washington, Homeland Security Secretary Janet Napolitano told a congressional committee in Washington Thursday that she wouldn't describe them as images of suspects "under technical terms." But, she added, the FBI definitely needs to talk with them and "we need the public's help in locating these individuals."
Napolitano said the federal investigation into the bombings is progressing yet it is too early to say if they are connected to a domestic or foreign terrorist plot.
"This is not an NCIS episode," she said. "Sometimes you have to take time to properly put the chain together to identiy the perpetrators, but everybody's committed to seeing that that gets done in the right way."
President Obama, who has called the bombings an act of terrorism, and his wife, Michelle, attended an interfaith healing service Thursday at Boston's Cathedral of the Holy Cross. The pews in the front of the church were filled with family and friends of the victims.
"Our prayers are with the injured -- so many wounded, some gravely," Obama said. "From their beds, some are surely watching us gather here today. And if you are, know this: As you begin this long journey of recovery, your city is with you. Your commonwealth is with you. Your country is with you. We will all be with you as you learn to stand and walk and, yes, run again. Of that I have no doubt. You will run again. You will run again.”
Afterwards, the president and first lady visited with injured victims and their doctors and nurses at three Boston hospitals. Obama also met with hundreds of first responders and race volunteers at Cathedral High School, praising them for embodying "the best of the American spirit."
Earlier, the president signed an emergency declaration to release federal funds to help Boston recover from the tragedy. More than 60 of the injured remain hospitalized, including a dozen in critical condition. Doctors reported that 15 children and adults had limbs amputated as a result of severe flesh, bone and blood vessel wounds.
Investigators believe the bombs were hidden in black duffel bags or backpacks, and constructed of common household pressure cookers packed with nails, ball bearings and buckshot-like BBs. They said they were detonated by timers or remote devices, causing metal shrapnel to spray spectators.
U.S. security officials said similar bombs have been used in terrorist attacks in India, Nepal, Pakistan and Afghanistan.
Killed in the Boston bombings from the metal projectiles was 8-year-old Martin Richard, of Boston. A widely distributed grade school photo of him holding a handmade poster saying, "No more hurting people. Peace," has become an international symbol of the tragedy.
Also killed in the blasts were Krystle Campbell, 29, a restaurant manager in Arlington, Mass., and Lu Lingz, 23, a Chinese national graduate student at Boston University.
President Obama, in his church remarks, assured their familes that authorities would find the bombers and make them face justice for their evil deed.
"We will find you," he said. "We will hold you accountable, but, more than that, our fidelity to our way of life, to a free and open society, will only grow stronger, for God has not given us a spirit of fear and timidity but one of power and love and self discipline.”