SAN FRANCISCO (AP) -- A former employee of Caltrain, a mass transit system that connects Silicon Valley with San Francisco, and a former contractor for the transit agency allegedly used public funds to build two small apartments for themselves inside two train stations, authorities said Thursday.

San Mateo County prosecutors charged Joseph Vincent Navarro, a former deputy director for Caltrain, and Seth Andrew Worden, a former employee of TransAmerica Services Inc., with a felony charge of misusing public funds, the Mercury News reported.

Navarro and Worden didn't immediately answer emails from The Associated Press seeking comment.

Worden, 61, was arraigned Wednesday and released on his own recognizance, court records show. Navarro, 66, was scheduled to be arraigned Friday, when Worden is set to make another court appearance, the newspaper reported.

Prosecutors said that between 2019 and 2020 Navarro allegedly conspired with Worden and approved $42,000 in building expenses to turn an office into a small apartment inside Caltrain's Burlingame train station.

The criminal complaint alleges that Worden used $8,000 in taxpayer funds to build himself similar living quarters inside the Millbrae train station, the newspaper reported.

Navarro and Worden allegedly ensured that no invoice surpassed $3,000, averting further authorization from Caltrain and TransAmerica Services Inc., the firm that employed Worden, prosecutors said.

Caltrain employees first discovered the converted space at the Millbrae station in 2020, authorities said. But the transit agency was unaware of Navarro's place in Burlingame until getting an anonymous tip in 2022, they said.

"The misuse of public funds for private use is a violation of the law, Caltrain policy and the public's trust," Caltrain Executive Director Michelle Bouchard said in a statement. "Caltrain investigates every claim of such misconduct, and in cases where there is evidence of unlawful conduct by an employee or a contractor, we immediately act to rectify the situation and hold the individuals who are responsible accountable."

Navarro was fired after being confronted with the tip, and reportedly admitted to "occasionally using the station as his residence," prosecutors said. Caltrain then alerted the district attorney's office about the potential for criminal charges.