THE FBI has released video footage and pictures of two Boston Marathon bombing suspects, according to new.com.au.

The website reports FBI Agent Richard DesLauriers said the images are from surveillance cameras near the explosion sites shortly before Monday's blasts at the world's most famous marathon. He said one suspect is believed to have planted the devices near the finish line.

Authorities had warned not to expect the case to be cracked quickly as they looked through a vast response to their plea for photos and video from the blast scene.

The images show two young-looking men wearing baseball caps, wearing jackets and carrying backpacks along the race route and weaving through the crowd.

Investigators have also gathered physical evidence, including scraps of black nylon and metal shards that were packed into a pressure cooker, believed to have been transported in a backpack.

The blasts killed 8-year-old Martin Richard, 29-year-old Krystle Campbell and Lu Lingzi, a graduate student from China. Seven victims remained in critical condition.

"For more than 100 years, the FBI has relied upon the public to be its eyes and ears,'' DesLauriers said. "Somebody out there knows these individuals.... Each piece moves us toward justice.''

More: news.com.au.