The first official images of the suspects in the Boston Marathon investigation have been released

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The images of the men, described as 'armed and extremely dangerous', were sourced from surveillance cameras that took the pictures just before the explosions.

The man in the black baseball has been dubbed suspect one, while the man in the white hat is suspect 2. Investigators believe the latter planted the bombs near the finish line.

FBI Agent Richard DesLauriers said: "Somebody out there knows these individuals as friends, neighbors, co-workers or family members of the suspects. Though it may be difficult, the nation is counting on those with information to come forward and provide it to us."

While the men are not seen talking to one another in the CCTV footage, the FBI believe the suspects were working together.