Six correctional officers were injured during an inmate attack at a California prison and sent to the hospital to be treated for those injuries, officials said.

State Department of Corrections and Rehabilitation spokesperson Terri Hardy said in a statement that some of the injuries the correctional officers sustained included potential broken bones, lacerations, and stab wounds.

Two inmates were also sent to outside hospitals for treatment while others were treated at the prison’s medical complex.

About 20 inmates were present in the recreation yard at the Richard J. Donovan State Prison complex around 3:55 p.m. when some of the inmates allegedly began attacking the corrections officers, according to the news release.

A warning shot was fired to ultimately stop the mayhem when other tactics of trying to stop the violence did not work. The inmates reportedly ignored the commands to stop before the shot was fired. Additional officers responded to the situation after the shot was fired.

NBC San Diego reported that an investigation is ongoing to find out how many inmates participated in the attack. The prison said those involved could each face one count of attempted murder of a peace officer.

Fox 5 San Diego reported that officers discovered several weapons following the attack. Officials say they are also not releasing the names of the inmates involved, due to the ongoing investigation.

The prison’s Investigative Service Unit will lead the investigation, and the inmates involved will be placed in different units.