A correctional officer at Sierra Conservation Center was assaulted by an inmate in Tuolumne County on Sunday, the California Department of Corrections and Rehabilitation said.

The employee was sent to the hospital, treated and released. The prison did not detail the circumstances of the attack.

CDCR said in a statement the inmate has been placed in restricted housing while under investigation.

“Due to the ongoing nature of the situation, we are unable to provide further details at this time. Our top priority is the safety and well-being of our staff. We appreciate your understanding and patience during this sensitive time,” CDCR said.

An investigation will determine potential charges and referral to the Tuolumne County District Attorney.