SALINAS, Calif. — Six doctors suspected of overbilling the state for medical and psychiatric services provided to inmates at Salinas Valley State Prison are facing charges of grand theft and presenting false claims.

At least five of the doctors pleaded not guilty Tuesday.

Authorities say five of the doctors submitted false invoices claiming they worked the whole day when they had only worked part of it.

The sixth doctor — 69-year-old Charles Lee of Salinas — is accused of signing timesheets he knew were fraudulent.

Authorities have identified the other doctors as 48-year-old Mark Herbst of Honolulu, 65-year-old David Hoban of Santa Cruz, 42-year-old Randy Sid of Pacific Grove, 60-year-old Wade Exum of Las Vegas and 43-year-old Pedro Eva of Soledad.