Republican lawmakers for eight months have been leading the probe into “Fast and Furious,” the controversial ATF gun operation, and trying to determine who in President Obama’s Justice Department knew what, and when they knew it.

But it turns out there was another gun operation run by the Bureau of Alcohol, Tobacco, Firearms and Explosives years before, using the same tactics of allowing guns to flow illegally onto U.S. streets and into Mexico. This operation was conducted under the Bush administration’s Justice Department.

Dubbed “Operation Wide Receiver,” the case was run out of Tucson between 2006 and 2007 and involved hundreds of guns that were purchased by small-time buyers who transferred them to middle men who then passed them up the chain and into Mexico.

ATF’s new acting director, B. Todd Jones, when asked by The Washington Post, said that Operation Wide Receiver was launched out of ATF’s Phoenix division — the same field office that oversaw Fast and Furious. ATF has said that Fast and Furious was an attempt to track more than 2,000 firearms and link them to Mexico’s Sinaloa drug cartel.

Jones said he did not know of any other cases where ATF knowingly allowed guns “to walk,” meaning they were allowed to pass into the black market or Mexico without ATF intervention. Jones said he could not discuss either case because they are both being investigated by the Justice Inspector General.

Operation Wide Receiver came to light when Rep. Darryl Issa (R-Calif.) and Sen. Charles E. Grassley (R-Iowa) released new documents and e-mails this week which they said showed that although Attorney General Eric H. Holder Jr. told Congress in May that he had just learned about Fast and Furious, he had known for about 10 months.

That alleged discrepancy led some Republican lawmakers to accuse Holder of perjury. They have pounded on Holder over Fast and Furious, in some cases calling for his resignation.Their investigation of the program has led to the reassignment of the former ATF director and others, and the resignation of the U.S. attorney in Arizona.

But Wide Receiver, conducted in the Bush administration, has not received a lot of attention. According to Justice spokeswoman Tracy Schmaler, some of the e-mails used in the attempt to discredit Holder were referring to the Tucson case, Wide Receiver.

More specifically, Schmaler said that when the e-mails mention “guns walking,” they are referring to the 2006-07 Tucson case, Operation Wide Receiver. Schmaler said neither of the officials knew about guns walking in the Fast and Furious case.

On Oct. 16, 2010, James Trusty, chief of the Organized Crime and Gang section, wrote to Criminal Division Deputy Assistant Attorney General Jason Weinstein:

“Looks like we’ll be able to unseal the Tucson case sooner than the Fast and Furious,” he wrote. “It’s not clear how much we’re involved in the main F and F case, but we have Tucson. . . . I’m not sure how much grief we get for ‘guns walking,’ it [sic] may be more like, ‘Finally, they’re going after people who sent guns down there.’ ”

The next day, Oct. 17, 2010, Weinstein replied:

“Do you think we should try to have Lanny [Breuer] participate in press when Fast and Furious and Laura’s Tucson case are unsealed?” he wrote. “It’s a tricky case given the number of guns that have walked but it is a significant set of prosecutions.” Breuer is the assistant attorney general for the Criminal Division.

Whether the issue was Operation Wide Receiver or Fast and Furious, Justice should have acknowledged the tactics to Congress when asked, said a spokesman for Issa. “In February, the Justice Department asserted to Congress it had no knowledge of gun walking by ATF agents,” said the spokesman, Frederick Hill.

Grassley staffers said Thursday night that it was Jason Weinstein, the Criminal Division deputy assistant attorney general, who was the lead Justice Department official who briefed the Senate Judiciary staff in February and left the impression that no gun walking had occurred.

Grassley and Issa released more documents Thursday, charging that Holder received at least five memos describing Fast and Furious, beginning in July 2010.

At a White House news conference, President Obama defended Holder and reiterated that neither he nor Holder knew that ATF was allowing illegally purchased guns to slip into Mexico.