TUCSON, Ariz. — Authorities made a rare disclosure Monday linked to the botched gun-smuggling investigation known as Operation Fast and Furious, revealing identities and requesting the public's help in capturing four fugitives accused in the shooting death of a U.S. Border Patrol agent 18 months ago.

The announcement comes in the wake of pressure from U.S. House Republicans who led a vote to hold Attorney General Eric Holder in contempt of Congress, criticizing the nation's top prosecutor for withholding information related to the probe.

"We believe it's in the best interest of this ongoing investigation to unseal the case at this point in time and to enlist the assistance of the general publics in both Mexico and the United States," said federal prosecutor Laura Duffy. She said the decision to release the information came independently and would not discuss the recent congressional action against Holder.

Operation Fast and Furious was launched in 2009 to catch trafficking kingpins, but federal agents lost track of about 1,400 of the more than 2,000 weapons – including AK-47s and other high-powered assault rifles.

Some of the guns purchased illegally with the government's knowledge were later found at crime scenes in Mexico and the U.S.

Critics have hammered federal authorities for allowing informants to walk away from Phoenix-area gun shops with weapons, rather than immediately arresting suspects and seizing firearms.

Since the fatal shootout near the U.S.-Mexico line in December 2010, deep flaws in the government's weapons trafficking case have come to light. Federal authorities have repeatedly declined to disclose information related to the death of Border Patrol Agent Brian Terry, such as what became of the gun used to kill him.

The release of the suspects' identities in a newly unsealed indictment Monday came with the offer of a $1 million reward for information leading to their capture.

The FBI says it is seeking information related to Jesus Rosario Favela-Astorga, 31, Ivan Soto-Barraza, 34, Heraclio Osorio-Arellanes, 34, and Lionel Portillo-Meza.

Portillo-Meza's age and birthplace were unavailable. The other three fugitives were born in Mexico, but their hometowns were not available.

Authorities had previously released the identity of the fifth suspect, Manuel Osorio-Arellanes, of El Fuerte in the Mexican state of Sinaloa. He was shot during the gunfight, and has been in custody since the night of the shooting. He has pleaded not guilty in the case, telling investigators that he raised his weapon toward the agents during the shootout but didn't fire, the FBI said in records.

His age was not immediately available.

All five have been charged with murder. They also face charges of assaulting four federal agents.

FBI agents declined to discuss which fugitive is suspected of firing the shot that killed Terry. They also would not comment on whether the weapon was linked to an Operation Fast and Furious purchase.

The five men, plus another who faces lesser charges in the case, came to the U.S. from Mexico in order to rob marijuana smugglers, the indictment said.

The disclosures are among the few details released by authorities despite repeated requests from congressional leaders and news organizations, including The Associated Press. The FBI, ATF, and U.S. Customs and Border Protection have all denied Freedom of Information Act requests that seek reports and other documents in the investigation of the shooting.

Patrick McGroder, an attorney for the Terry family, said in a statement that Monday's information shows that the prosecution is moving forward, but efforts to hold federal officials accountable for the flawed investigation remain stalled.

McGroder says Holder's office should release the documents sought by members of Congress.

Agent Terry "and his family rightly deserve a full and thorough explanation of how Operation Fast and Furious came to be," McGroder said.

Terry, a former Marine and Michigan police officer, was part of an elite squad similar to a police SWAT team that was sent to the remote areas north of Nogales known for border crime, drug smuggling and violence.

FBI Special Agent James Turgal said in announcing the reward that "we stand in support of the Terry family and our partners in Border Patrol."

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Associated Press writer Jacques Billeaud contributed from Phoenix.

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  • From left, House Minority Whip Steny Hoyer of Md., Rep. Maxine Waters, D-Calif., Rep. John Lewis, D-Ga., Rep, Charles Rangel, D-N.Y., and House Minority Leader Nancy Pelosi of Calif., right, and many House Democrats walk out of the Capitol during the vote to hold Attorney General Eric Holder in contempt, Thursday, June 28, 2012, on Capitol Hill in Washington. (AP Photo/J. Scott Applewhite)

  • House Oversight and Government Reform Committee Chairman Rep. Darrell Issa, R-Calif., left, and the committee's ranking Democrat Rep. Elijah Cummings, D-Md., go to the House Rules Committee, on Capitol Hill in Washington, Wednesday, June 27, 2012, to argue procedures as the House of Representatives prepares to vote on whether Attorney General Eric Holder is in contempt of Congress because he has refused to give the Oversight Committee all the documents it wants related to Operation Fast and Furious, the flawed gun-smuggling probe involving Mexican drug cartels. (AP Photo/J. Scott Applewhite)

  • Rep. Carolyn Maloney, D-N.Y., left, stretches out her hand to get the attention of Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, as the panel considers a vote to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. Rep. Elijah Cummings, D-Md., the ranking member, sits between them. (AP Photo/J. Scott Applewhite)

  • WASHINGTON, DC - JUNE 20: House Oversight and Government Reform Chairman Darrell Issa (R-CA) (C) talks with raking member U.S. Rep. Elijah Cummings (D-MD) (L) during a mark up hearing on Capitol Hill June 20, 2012 in Washington, DC. Issa and the committee Republicans called the hearing to vote on holding U.S. Attorney General Eric Holder in contempt of Congress for refusing to hand over documents the GOP says are key to their investigation into the failed Fast and Furious operation. Before the start of the hearing, the White House asserted the documents are protected by executive privilidge. (Photo by Chip Somodevilla/Getty Images)

  • Rep. Darrell Issa, R-Calif., center, chairman of the House Oversight and Government Reform Committee, confers with an aide as the panel considers a vote to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. Rep. Elijah Cummings, D-Md., the ranking member, second from left, speaks with Rep. Carolyn Maloney, D-N.Y., who authored an amendment in support of Holder. In a showdown with President Barack Obama's administration, House Republicans had pressed for more Justice Department documents on the flawed gun-smuggling probe known as Operation Fast and Furious that resulted in hundreds of guns illicitly purchased in Arizona gun shops winding up in the hands of Mexican drug cartels. (AP Photo/J. Scott Applewhite)

  • Rep. Jason Chaffetz, R-Utah, center, debates Rep. Stephen Lynch, D-Mass., as the House Oversight and Government Reform Committee considers a vote to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. (AP Photo/J. Scott Applewhite)

  • The House Oversight and Government Reform Committee, led by Chairman Darrell Issa, R-Calif., right, considers whether to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. Rep. Elijah Cummings, D-Md., the ranking member, speaks at left. In a showdown with President Barack Obama's administration, House Republicans are pressing for more Justice Department documents on the flawed gun-smuggling probe known as Operation Fast and Furious that resulted in hundreds of guns illicitly purchased in Arizona gun shops winding up in the hands of Mexican drug cartels. (AP Photo/J. Scott Applewhite)

  • WASHINGTON, DC - JUNE 20: House Oversight and Government Reform raking member U.S. Rep. Elijah Cummings (D-MD) (R) hears from U.S. Rep. Dennis Kucinich (D-OH) during a mark up hearing with June 20, 2012 in Washington, DC. Chairman Darrell Issa (R-CA) and the committee Republicans called the hearing to vote on holding U.S. Attorney General Eric Holder in contempt of Congress for refusing to hand over documents the GOP says are key to their investigation into the failed Fast and Furious operation. Before the start of the hearing, the White House asserted the documents are protected by executive privilidge. (Photo by Chip Somodevilla/Getty Images)

  • Attorney General Eric holder speaks to reporters following his meeting on Capitol Hill in Washington, Tuesday, June 19, 2012. Holder wants a House panel to drop plans to try to hold him in contempt of Congress, and the panel's chairman wants more Justice Department documents regarding Operation Fast and Furious, a flawed gun-smuggling probe in Arizona. Holder and Rep. Issa met in an effort to resolve their dispute over the investigation of Fast and Furious by the House Oversight and Government Reform Committee that Issa chairs.(AP Photo/Susan Walsh)

  • Rep. Darrell Issa, R-Calif., speaks to reporters following his meeting with Attorney General Eric Holder on Capitol Hill in Washington, Tuesday, June 19, 2012. Holder wants a House panel to drop plans to try to hold him in contempt of Congress, and the panel's chairman wants more Justice Department documents regarding Operation Fast and Furious, a flawed gun-smuggling probe in Arizona. Holder and Issa met in an effort to resolve their dispute over the investigation of Fast and Furious by the House Oversight and Government Reform Committee that Issa chairs. (AP Photo/Susan Walsh)

  • Attorney General Eric Holder speaks to reporters following his meeting on Capitol Hill in Washington, Tuesday, June 19, 2012. Holder wants a House panel to drop plans to try to hold him in contempt of Congress, and the panel's chairman wants more Justice Department documents regarding Operation Fast and Furious, a flawed gun-smuggling probe in Arizona. Holder and Rep. Darrell Issa, a California Republican, met in an effort to resolve their dispute over the investigation of Fast and Furious by the House Oversight and Government Reform Committee that Issa chairs. (AP Photo/Susan Walsh)

  • Attorney General Eric Holder walks through Statuary Hall to speak to reporters following his meeting on Capitol Hill in Washington, Tuesday, June 19, 2012. (AP Photo/Susan Walsh)

  • FILE -In this Dec. 8, 2011 file photo, House Judiciary Committee member Rep. Darrell Issa, R-Calif., left, shakes hands with Attorney General Eric Holder on Capitol Hill in Washington. Holder is proposing to meet with Issa by Monday to settle a dispute over Justice Department documents the congressman is demanding on a flawed gun-smuggling probe. (AP Photo/Susan Walsh, File)