WASHINGTON – Federal authorities have launched a search for a "substantial" number of firearms and gun parts that they say were stolen from a government disposal facility, officials said Wednesday.

A security contractor assigned to the Bureau of Alcohol Tobacco Firearms and Explosives' repository in Martinsburg, West Virginia has been charged in connection with the missing weapons and parts. A search of his vehicle earlier this month allegedly yielded a pistol that had been registered in the government's archives of retired weapons in 2017.

Christopher Yates, a contract security guard for the ATF in West Virginia, has been charged with possession of a stolen firearm and theft of government property.

In an interview with ATF agents late last month, Yates also allegedly acknowledged transferring at least some of the stolen property to an unidentified person Maryland.

Yates' attorney, Nicholas J. Compton, declined to comment Wednesday.

ATF spokeswoman April Langwell described the theft as involving a "substantial" number of firearm parts and ammunition, including slides and barrels from retired ATF service weapons, but would not specify how many or where investigators believe they have ended up. Outside of the ATF, the materials are mostly unregulated and available for purchase online without a background check.

The search for the missing weapons was first reported by CBS News.

Langwell said the parts were likely sold to people who did not know they were stolen. She said the ATF first learned of the theft when a local law enforcement agency asked the ATF to trace a gun part it had recovered.

"ATF has made substantial progress in recovering the stolen property and is working around the clock to pursue all leads," the agency said in a statement.

The ATF has faced scrutiny before after the agency acknowledged that it allowed more than 2,000 weapons to stream into Mexico as part of a botched undercover operation. One of the weapons was found at the scene of a fatal shooting of Border Patrol agent Brian Terry.