The FBI on Thursday released images and videos showing two suspects whom authorities believe carried out Monday's attack at the Boston Marathon. 

The FBI asked the public for help in identifying the two suspects, adding that law enforcement officials had already been aided by thousands of tips.

According to Special Agent Richard DesLauriers, the lead investigator in the case, authorities initially identified a single person of interest by combing through surveillance footage they had obtained. When they looked more closely at the first individual, they discovered a second suspect who appeared to be working in concert with him.

Both suspects are seen wearing baseball caps and carrying backpacks. Suspect 1 is wearing the black cap; Suspect 2 the white cap. According to the FBI, surveillance footage (which has not been released) shows Suspect 2 dropping his backpack near the site of one of the explosions. 

Authorities had already revealed that they believed the explosives used in the attacks were shrapnel-packed pressure cookers stowed in backpacks.

Authorities added that both men are believed to be armed and dangerous, and advised the public to not take any sort of vigilante action. Instead, the FBI has asked that anyone with information about either of the two men email, or call the agency at 1-800-CALL-FBI (1-800-225-5324).

On Wednesday, speculation swirled as to whether investigators had identified — or possibly even apprehended — a suspect in the case. Investigators quickly shot down reports that they'd arrested someone, but indicated they'd had a major break in the case thanks to newfound surveillance footage.

That speculation spilled over into Thursday, when the New York Post ran a front page image showing two men — not the two whom the FBI identified today — with a caption suggesting they were the two suspects. Internet sleuths and other media outlets quickly identified one of the two men, and the Post later reported that both had been questioned by investigators and found innocent.