Authorities have released photos of two men they believe are responsible for the Boston Marathon bombings.
FBI officials held a press conference just after 4 p.m. Thursday.
The deadly explosions claimed three lives but left some 180 people wounded.
Many of those injured required their legs to be amputated.
FBI Agent Richard DesLauriers said one the suspects is believed to have planted the devices near the finish line of the race.
Investigators said both suspects are to be considered armed and extremely dangerous.
Anyone with visual images, video and/or details regarding the explosions along the Boston Marathon route and elsewhere, is asked submit them on https://bostonmarathontips.fbi.gov/.
Witnesses can also call 1-800-CALL-FBI (1-800-225-5324), prompt #3, with information.
FBI officials said no piece of information or detail is too small.