A California state mailroom worker pleaded guilty Feb. 27 to stealing thousands of dollars in diamonds and coins while on the job, according to a statement from the Sacramento County District Attorney’s Office.

Diamonds worth $300,000 had been reported missing from the State Controller’s Office mailroom in Sacramento, the statement said.

According to prosecutors, Miguel Espinosa, who had worked in the mailroom for more than a decade, had been stealing the jewelry for seven years. Prosecutors said the items were unclaimed property.

Video from surveillance cameras showed Mr. Espinosa carried out the burglaries by moving a package containing diamonds from the mailroom to a nearby room with no surveillance cameras, then brought the package back to the mailroom. He resealed the package, then put it in the mail for delivery.

Authorities searched Espinosa’s home and found the stolen diamonds and coins.

Prosecutors said in the statement 10 people had been victimized by the burglaries. Authorities have not released any further details about the origin of the packages.

On April 4, Mr. Espinosa will be sentenced to 3 years and 4 months in prison, prosecutors said.