By Jake Tapper, Devin Dwyer and Jason Ryan

A new report by our partners at Univision has found additional links between violent crimes in Mexico and guns involved in the Obama administration's flawed "Fast and Furious" operation.

Fifty-seven previously unidentified weapons tied to the operation - allowed to "walk" across the U.S. border into Mexico so ATF agents could trace them - were later found at the sites of murders, kidnappings and at "two gruesome massacres," Univision's Gerardo Reyes and Santiago Wills report .

The reporters made the discovery by cross-referencing a list of guns registered with "Fast and Furious" and a Mexican government list of the roughly 60,000 guns recovered at crime scenes in 2009 and 2010.

In July, a congressional investigation into the program reported 122 weapons had been traced to Mexican crime scenes. The Univision report adds 57 weapons to that list.

Asked for comment on the report, a Justice Department official noted to ABC News that the Attorney General "testified several times about the tragic consequences of this flawed investigation" and that he "put a stop to these flawed field tactics that began many years ago (2006) and instituted new leadership at ATF as well as key reforms that require stronger oversight of investigations."

Holder has testified that about 800 weapons - mostly AK-47s and high-powered handguns - had been recovered from "Fast and Furious." An estimated 1,200 guns from the program are still unaccounted for.

Last month the Justice Department Inspector General released a 450-page report documenting shortcomings of the gun-walking program and administration oversight of it since its initiation in October 2009. The program has since been discontinued.