The FBI has released photos of two suspects sought in the Boston Marathon bombings, and investigators are asking the public to help identify them.
FBI Agent Richard DesLauriers said the photos came from surveillance cameras, photos and other evidence near the explosion sites. He also said that finding the two men is the FBI's No. 1 priority.
"After a detailed analysis, we are releasing video of the two suspects, calling them 'one' and 'two,' DesLauriers said. "They appear to be associated."
DesLauriers said one the suspects is believed to have planted the devices near the finish line of the race. He says both suspects are considered armed and extremely dangerous, and he warns members of the public to avoid trying to contact them. Instead, anyone with a tip is urged to contact law enforcement directly.
The FBI also set up a website dedicated to collecting tips at: https://bostonmarathontips.fbi.gov/
Anyone with a tip can also call 1-800-225-5324.
"Somebody knows them as friends, family members and co-workers," DesLauriers said. "Though it may be difficult, the nation is counting on them."
One of the things DesLauriers emphasized repeatedly during the photo release was that investigators want only these specific images to be used. Although there are other images online, officials say those are only muddying matters and confusing people.
Clearly, the FBI is hoping the images become a viral sensation. Over the past four days, several cyber-sleuths have been combing through countless images in online forums. Now, investigators are hoping they'll devote their attention to the surveillance photos.
"Other photos should not be deemed credible and they only divert attention and resources of law enforcement," DesLauriers said.
The two men seem remarkably calm and methodical in video footage released by the FBI, both were carrying heavy backpack packs -- including one that is strikingly similar to the backpack that held the first bomb.
The video shows the two casually stroll in single file toward the finish line 12 minutes before the bombs exploded.
Investigators did not release video surveillance footage that shows the second suspect, who can be seen wearing a white hat, putting a backpack on the ground just minutes before the second blast. DesLauriers said he then continued heading west on Boylston Street but apparently stayed nearby to watch the aftermath.
The FBI is also trying to track down where the pressure cookers, batteries and electronics used to make the bombs came from.
Investigators did not comment on the suspects' ethnicity or any possible motive, foreign or domestic.
The explosions Monday killed three people and injured more than 180.
The images were released hours after President Barack Obama and first lady Michelle Obama attended an interfaith service at a Roman Catholic cathedral in Boston to remember the victims, including an 8-year-old boy.
Watch the FBI-released video on YouTube: http://youtu.be/M80DXI932OE
High-resolution images: http://www.fbi.gov/news/updates-on-investigation-into-multiple-explosions-in-boston/photos
Information from the Associated Press was used in this report.