Boston police and Massachusettes State Police are asking anyone with photographs or video of the finish line at the Boston Marathon to send them in just in case a clue can be found.
At a Tuesday morning news conference, police and federal agents repeatedly appealed for any video, audio and photos taken by marathon spectators, even images that people might not think are significant.
"There has to be hundreds, if not thousands, of photos and videos'' that might help investigators, state police Col. Timothy Alben said.
three people died and more than 100 people injured; at least 17 critically, police said. At least eight children were being treated at hospitals. In addition to losing limbs, victims suffered broken bones, shrapnel wounds and ruptured eardrums.
One of the newest videos to surface was shot by Jennifer Treacy of New York State.
She told NBC Bay Area she was running in her very first marathon and wanted to record some of the sights and scenes of the race.
“I happened to be filming the crowd at various points in the race and I got to the finish line I was videoing and at that point the explosion happened," Treacy said.
At first, she thought she was seeing fireworks but “it quickly became clear it was a bomb because it was so big and it shook the ground and there was so much smoke and people screaming and running.
Treacy left the street into a nearby building and called her family.
Her husband and children were following her along the racecourse.
“They saw me at mile 22. And I knew they were headed to the finish line to meet there. I did not know where they were. But they were on the T (the local subway system) when the bomb went off. I was able to get ahold of my husband and say ‘do not take it any further towards the finish line.”
Boston Police Commissioner Edward Davis said investigators also gathered a large number of surveillance tapes from businesses in the area and intend to go through the video frame by frame.
"This is probably one of the most photographed areas in the country yesterday,'' he said.