OKLAHOMA CITY (AP) — An Oklahoma City police officer charged with concealing a federal crime and lying to investigators looking into an interstate theft ring now faces an additional charge of conspiracy.

An indictment filed Tuesday says a grand jury added the conspiracy count against 25-year-old Weston Slater. Slater is one of six people charged with stealing various vehicles in Kansas, Texas, Missouri and Nebraska and bringing them to Oklahoma to sell.

Slater has pleaded not guilty to the earlier charges and is on unpaid leave from the department. A message left with his attorney Thursday wasn’t immediately returned.

The indictment alleges Slater used a police computer to determine whether a pickup truck had been stolen in Texas, warned a co-defendant of the law enforcement investigation and lied to the FBI during the investigation.