Updated at 5:36 p.m. ET
(CBS/AP) The Justice Department's inspector general cleared Attorney General Eric Holder Wednesday of knowing about the gun-walking operation known as Fast and Furious that allowed thousands of weapons to cross into Mexico.
But Inspector General Michael Horowitz concluded that there were "serious failures" at both the Justice Department and its Bureau of Alcohol, Tobacco, Firearms and Explosives going back more than six years, CBS Radio News reporter Stephanie Lambidakis reports.
Horowitz found that no one running the operations -- not agents, nor prosecutors, nor managers -- questioned the wisdom of letting guns vanish across the border with Mexico, where they ended up in the hands of drug traffickers.
Two of the 2,000 weapons thought to have been acquired by illicit buyers in the Fast and Furious investigation were recovered at the scene of a 2010 shootout with drug traffickers that claimed the life of U.S. border agent Brian Terry. About 1,400 of the total have yet to be recovered.
In his 471-page report, Horowitz referred more than a dozen people for possible department disciplinary action for their roles in Fast and Furious and a separate, earlier probe known as Wide Receiver, undertaken during the George W. Bush administration.
Gun-walking was an experimental tactic, barred under long-standing department policy. ATF agents in Arizona allowed suspected "straw purchasers," in these cases believed to be working for Mexican drug gangs, to leave Phoenix-area gun stores with weapons in order to track them and bring charges against gun-smuggling kingpins who long had eluded prosecution.
Lambidakis reports that between November 2009 and mid-April 2010, straw buyers purchased approximately 1,300 firearms for more than a million dollars, "yet agents made no arrests and just a single seizure," the report states.
Because of thin ATF staffing and weak penalties, the traditional strategy of arresting suspected straw buyers as soon as possible had failed to stop the flow of tens of thousands of guns to Mexico more than 68,000 in the past five years. The operation was a response to criticisms of the agency's anti-smuggling efforts.
The inspector general found fault with the work of the senior ATF leadership, the ATF staff and U.S. attorney's office in Phoenix and senior officials of Justice's criminal division in Washington. He also said that poor internal information-gathering and drafting at Justice and ATF caused the department to initially misinform Congress about Fast and Furious.
Fast and Furious has produced charges against 20 gun traffickers, 14 of whom have pleaded guilty so far.
Two senior officials left the department, one by resignation and one by retirement, with the report's release.
While Horowitz heaped most of the blame for Fast and Furious on investigators in Phoenix, one senior official, Deputy Assistant Attorney General Jason Weinstein, is blamed for not acting to stop the tactics.
"Weinstein was the most senior person in the department in April and May 2010 who was in a position to identify the similarity between the inappropriate tactics used in Operations Wide Receiver and Fast and Furious," the report said. ATF agents in Arizona conducted Wide Receiver in 2006 and 2007 and began Fast and Furious in October 2009.
Weinstein resigned Tuesday night, CBS Radio News reports. Weinstein's lawyer, Michael Bromwich, called the report's criticism "profoundly wrong" and "deeply flawed."
In a statement released Wednesday, Holder said: "Jason has dedicated much of his career to fighting violent crime and has led highly successful efforts around the country in this effort. The American people are safer because of his work."
One of those criticized in the report, former ATF acting director Kenneth Melson, who headed that office during the Fast and Furious investigation, retired upon release of the report.
"Melson made too many assumptions about the case," the report stated. "Melson should have asked basic questions about the investigation, including how public safety was being protected."
Melson responded in a written statement: "While I firmly disagree with many of the speculative assumptions, conclusions and characterizations in the inspector general's report, as the acting director of the agency I was ultimately responsible for the actions of each employee."
The report did not criticize Holder, but said lower-level officials should have briefed him about the investigation much earlier. The inspector general also said he found no evidence that former Attorney General Michael Mukasey, who took office late in the Bush administration after Wide Receiver was ended, was ever informed that it used gun-walking.
Holder, who the Republican-led House of Representatives cited for contempt in a dispute over Fast and Furious documents earlier this year, said that the report was "consistent" with what he's said about the botched operation.
"It is unfortunate that some were so quick to make baseless accusations before they possessed the facts about these operations - accusations that turned out to be without foundation and that have caused a great deal of unnecessary harm and confusion," Holder said. "I hope today's report acts as a reminder of the dangers of adopting as fact unsubstantiated conclusions before an investigation of the circumstances is completed."
The report found no evidence that Holder was informed about the Fast and Furious operation before Jan. 31, 2011, or that the attorney general was told about the much-disputed gun-walking tactic.