The FBI 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.
The announcement came as the Justice Department unsealed an indictment charging the four men, along with a fifth already in custody, in the death of Brian Terry. Terry was shot back in 2010 while on patrol in Arizona.
His death gained national attention after it was discovered that two weapons at the crime scene came from the government's botched Fast and Furious gun-smuggling operation. In the operation, federal agents lost track of about 1,400 of the more than 2,000 weapons - including AK-47s and other high-powered assault rifles.
The announcement also came in the wake of pressure from U.S. House Republicans, who led a vote to hold Attorney General Eric Holder in contempt of Congress. They say Holder withheld information related to a probe into Operation Fast and Furious.
The Associated Press contributed to this report.