Four people, including one officer, were transported to an outside hospital, treated and released, following a riot involving about 40 inmates at Alder Creek Conservation Camp on Monday.

The riot occurred at about 5 p.m. when staff orders to the inmates to stop fighting were ignored, according to a California Department of Corrections and Rehabilitation press release. Staff used pepper spray and physical force to quell the incident and called 911.

Multiple agencies assisted, including the Del Norte County Sheriff's Office, the California Highway Patrol, the National Park Service and CALFIRE, according to the release.

The cause of the riot is still under investigation, according to the press release.

One corrections staff member was struck in the head and torso and was transported to an outside hospital for treatment. He has been released and is recovering at home, according to the press release.

Three inmates were also transported to the hospital with minor injuries and have been treated and released, according to the press release.

The inmates who initiated the incident have been placed in administrative segregation at Pelican Bay State Prison, according to the press release.

Alder Creek Conservation Camp is operated jointly by CDCR and CALFIRE and provides inmate firefighting crews for suppression activities in Humboldt and Del Norte counties. Inmates also perform conservation and community projects in the area.

The camp houses about 100 minimum-security inmates and employs nine CDCR staff members and 14 CALFIRE staff members, according to the press release.