Newly released e-mails in the controversy over the Fast and Furious gun-trafficking operation show that the program had been mentioned to a White House official, but the un­or­tho­dox tactics used by federal agents were not revealed in the documents.

Congressional investigators looking into the operation have been probing whether high-level Obama administration officials were aware of Fast and Furious.

The e-mails reveal that William Newell, former head of the Phoenix office of the Bureau of Alcohol, Tobacco, Firearms and Explosives, briefed Kevin O’Reilly on the Obama administration’s broader operations against Mexican gun traffickers. O’Reilly, a State Department official who had been detailed to the National Security Council at the White House, then shared the information with two other officials, including Dan Restrepo, President Obama’s senior adviser on Latin America.

The e-mails, turned over by the Justice Department to congressional investigators and obtained by The Washington Post, did not include details of the Fast and Furious operation, an ambitious plan to follow guns bought by illegal “straw purchasers” through middlemen and into the hierarchy of the Sinaloa Mexican drug cartel.

The exchanges add to a voluminous trail of documents and testimony in the long-running debate over Fast and Furious, which is the subject of a congressional investigation and an inquiry by the Department of Justice’s inspector general.

In one February e-mail to O’Reilly, Newell referred to Fast and Furious, the now-defunct operation that allowed some 2,000 illegally purchased firearms to hit the streets. The congressional inquiry began after it was revealed that a U.S. Border Patrol agent was killed in a gunbattle in which Fast and Furious guns were found at the scene.

Several other Newell e-mails referred to a large federal investigation along the southwest border. The e-mails did not specify the operation’s name, but U.S. officials said it probably was Fast and Furious.

Newell was clearly proud of his “very large ” case, but in one e-mail he made it clear he could not discuss details because it was an ongoing criminal investigation.

The e-mails “validate what we’ve said all along: that no one at the White House knew about the investigative tactics used in this operation, let alone letting anyone walk guns,’’ said a senior administration official, who spoke on condition of anonymity to discuss internal communications.

Yet the disclosure of even peripheral White House involvement in the Fast and Furious imbroglio could ratchet up political pressure on the administration from congressional Republicans.

Becca Glover Watkins, a spokeswoman for Rep. Darrell Issa (R-Calif.), chairman of the House Committee on Oversight and Government Reform, said committee investigators are “examining the role of White House officials in Operation Fast and Furious, including concerns that their interactions with ATF personnel may have undermined the chain of command in a law enforcement operation and increased risks to public safety.’’

But it was unclear if the cascading revelations of who knew about the ill-fated operation would continue. U.S. officials said they have found no further evidence of any White House knowledge of Fast and Furious, and Obama has said that he and Attorney General Eric H. Holder Jr. would never have approved the tactics used in the operation.

The officials characterized the e-mails between Newell and O’Reilly as a “back-channel communication” between two old friends who had worked together in the 1990s.

Paul Pelletier, a lawyer for Newell, who is now working at ATF headquarters in Washington, said Newell’s e-mails provided “public or soon-to-be public information about the state of gun trafficking along the southwest border. No operational plans were divulged.”

The e-mails follow a major shake-up at the Justice Department stemming from Fast and Furious. Kenneth E. Melson, acting director of the ATF, was reassigned to department headquarters this week. Dennis Burke, the U.S. attorney in Phoenix, resigned, and one of his prosecutors has been reassigned.

Law enforcement officials have said no further high-level changes are planned, and Melson, another senior ATF official and Burke have told congressional investigators that senior Justice officials were unaware of the tactics used in Fast and Furious.

The single e-mail that mentions Fast and Furious by name, sent from Newell to O’Reilly in February, cites an indictment stemming from the operation that had already been publicly released. “The first attachment is the press release, which goes into some detail of the other cases,’’ Newell wrote. “The Fast and Furious indictment is listed under U.S. v. Avila . . . all of these have been unsealed, they were unsealed the day of the press conference.’’