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 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 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 United States.

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.

The fugitives allegedly were members of a “rip-off crew” of Mexican bandits preying on illegal drug couriers in a remote canyon just north of the U.S.-Mexico border.

Border Patrol Agent Brian Terry and his team happened upon them. He was killed in a firefight that began with U.S. agents firing bean bags and ended with the bandits allegedly firing semiautomatic weapons. Two of their firearms, both AK-47s, were recovered and traced back to the ATF’s failed Fast and Furious gun-tracking operation, McClatchy News Service reported.

The four new defendants, all described as Mexican nationals, allegedly fled that night, leaving the two weapons behind.

Since the fatal shootout 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 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.

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.