April 18, 2013 -- Federal agents suspect components of a toy DuraTrax radio-controlled car were used to construct the bombs that exploded at the Boston Marathon Monday, according to four local hobby store owners and managers interviewed by the agents.
Store owners in Massachusetts and across the border in New Hampshire told ABC News federal agents questioned them about sales of a 1.25 volt Tenergy battery used in remote and radio-controlled cars, the same kind of battery shown in evidence photos from the scene of Monday's bombing.
FBI agents also made inquires at California-based Tenergy, which makes the battery packs specifically for use in DuraTrax toy cars, a company official said.
The bombs, at least one of which was housed in a common pressure cooker, claimed three lives and injured more than 170 others near the finish line of the race Monday afternoon. No group, domestic or international, has claimed responsibility, though law enforcement sources told ABC News today they have spotted two potential suspects.
There are instructions for creating a bomb using toy car parts online. A similar tactic was reportedly used in the attempted car bombing of a Michigan attorney in 2011.
Greg Faith, owner of Inside Out Hobbies in New Hampshire, said that when he saw the evidence pictures on television, he immediately recognized the batteries and other parts used in radio-controlled cars.
"An item that was first used for pleasure has now been used for devastation. It's just heartbreaking," he said. "He [the bomber] may have come here. it's horrifying."
After seeing their batteries in the evidence images, officials at Tenergy released a statement in which they said they were "deeply saddened" by the tragedy and noted their products are "commonly used by hobbyists for various toys including radio controlled cars, trucks, etc."
The product, the company said, "is a widely available retail product, that can be purchased… from multiple stores in the U.S., as well as online" for just a "few dollars."
The search for the store where the bomber may have purchased the battery is one of several leads FBI and law enforcement agents are tracking, including surveillance footage that has been used to spot two potential suspects.
Sources close to the investigation told ABC News investigators are also analyzing cell phone call records for any suspicious calls around the time of the attack or any of those made right at the time of the explosion, a possibly significant clue should authorities discover the bombs were remotely detonated.
Both DuraTrax and the FBI did not immediately respond to request for comment for this report.