House Republicans are calling for a special counsel to determine whether Attorney General Eric Holder misled Congress during his testimony to the House Judiciary Committee on Operation Fast and Furious, Fox News has learned.

House Judiciary Committee Chairman Lamar Smith, R-Texas, was sending a letter to President Obama on Tuesday arguing that Holder cannot investigate himself, and requesting the president instruct the Department of Justice to appoint a special counsel.

The question is whether Holder knowingly made false statements of fact under oath during a Judiciary Committee hearing on May 3. At the time, Holder indicated he was not familiar with the Bureau of Alcohol, Tobacco, Firearms and Explosives program known as Fast and Furious until about April 2011.

"I'm not sure of the exact date, but I probably heard about Fast and Furious for the first time over the last few weeks," Holder testified.

The Department of Justice defended Holder in a statement Tuesday.

“The Attorney General’s testimony to both the House and the Senate was consistent and truthful," it read. "He said in both March and May of this year that he became aware of the questionable tactics employed in the Fast and Furious Operation in early 2011 when ATF agents first raised them publicly, and at the time, he asked the Inspector General’s office to investigate the matter."

However, newly discovered memos suggest otherwise. For instance, one memo dated July 2010 shows Michael Walther, director of the National Drug Intelligence Center, told Holder that straw buyers in the Fast and Furious operation "are responsible for the purchase of 1,500 firearms that were then supplied to the Mexican drug trafficking cartels."

Other documents also indicate that Holder began receiving weekly briefings on the program from the National Drug Intelligence Center "beginning, at the latest, on July 5, 2010," Smith wrote.

"These updates mentioned, not only the name of the operation, but also specific details about guns being trafficked to Mexico," Smith wrote in the letter to Obama.

"Allegations that senior Justice Department officials may have intentionally misled members of Congress are extremely troubling and must be addressed by an independent and objective special counsel. I urge you to appoint a special counsel who will investigate these allegations as soon as possible," Smith wrote.

House Judiciary Committee Ranking Member John Conyers, D-Mich., said he had not been informed of the reqeest before it was sent to the president.

This is the third time in two years the Judiciary Committee chairman has called for a special counsel. In October 2009, Smith asks for a special counsel to investigate the now defunct community organizing group ACORN. In July 2010, Smith asked the Obama administration for a special counsel to investigate voter intimidation charges against the New Black Panther Party.

In response to the release of the memos, a Justice Department official said that the attorney general "has consistently said he became aware of the questionable tactics in early 2011 when ATF agents first raised them publicly, and then promptly asked the (inspector general) to investigate the matter."

The official added that in March 2011, Holder testified to a Senate Appropriations subcommittee of that development, and regularly receives hundreds of pages, none of which contained information on potential problems with Fast and Furious.

"The weekly reports (100 + pages) are provided to the office of the AG and (deputy attorney general) each week from approximately 24 offices and components. These are routine reports that provide general overviews and status updates on issues, policies, cases and investigations from offices and components across the country. None of these reports referenced the controversial tactics of that allowed guns to cross the border," the official said.

"(House Oversight and Government Reform Committee Chairman Darrell) Issa of all people, should be familiar with the difference between knowing about an investigation and being aware of questionable tactics employed in that investigation since documents provided to his committee show he was given a briefing that included the fast and furious operation in 2010 – a year before the controversy emerged," the official continued.

Issa, R-Calif., told Fox News on Tuesday that Holder saying he didn't understand the question rather than he didn't know of the program is not a successful defense to perjury.

Sen. Charles Grassley, R-Iowa, ranking Republican on the Senate Judiciary Committee, added that months before Holder testified -- on Jan. 31 -- he came to Grassley's office, where Grassley gave him a letter detailing the investigation of Fast and Furious.

"If he read my letter, he knew on January 31," Grassley told Fox News. "He probably actually knew about it way back in the middle of last year or earlier.

Grassley said since he's not a lawyer he's not going to make a judgment on whether Holder committed perjury.

"But I can tell you this. They're doing everything they can, in a fast and furious way, to cover up all the evidence or stonewalling us. But here's the issue, if he didn't perjure himself and didn't know about it, the best way that they can help us, Congressman Issa and me, is to just issue all the documents that we ask for and those documents will prove one way or the other right or wrong."

Smith said he was not suggesting that Holder committed perjury, per se.

"I am suggesting there is a conflict between what the attorney general told us and what these documents that were just released show us. ... We need to find out what's behind that ... and give the attorney general the opportunity to tell the truth," Smith told Fox News.

Fox News' Chad Pergram contributed to this report.