TUCSON, Ariz. (AP) — 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.

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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.