A riot involving nearly 50 inmates at Richard J. Donovan Correctional Facility left 10 prisoners wounded Friday, including one so severely that he had to be life-flighted from the prison, officials confirmed.

Several fights erupted simultaneously on the South Bay prison's yard for medium-custody prisoners at about 9 a.m. Friday, the California Department of Corrections and Rehabilitation (CDCR) said.

CDCR Capt. Philip Bracamonte said guards responded with orders for the prisoners to stop and when that didn't work, pepper spray was used on the inmates to try to break up the fights.

No lethal force was used, Bracamonte said.

At a news briefing Friday afternoon, Bracamonte estimated the riot had lasted about three minutes until, in his words, guards were able to "stop inmates and get them down."

"Inmates eventually did comply and stopped their combative behavior," he added.

NEW INFO: Per State Dept of Corrections. 50 inmates involved in riot at Donovan. Started when several fights and attacks broke out at same time. 10 inmates injured. 1 with serious head injury. No guards were injured. No lethal force used. Homemade weapons recovered. #nbc7 pic.twitter.com/8Xl09TCXLa — Artie Ojeda (@ArtieNBCSD) February 15, 2019

Patrick Walker, Battalion Chief of Cal Fire in the Otay Mesa area said his agency responded to the prison and quickly elevated its response, calling on additional agencies for backup including the San Diego Fire-Rescue Department, Chula Vista Fire Department, the CDRC, San Diego County EMS Bureau and Mercy ambulance and air ambulance.

In all, the battalion chief said crews transported 10 patients to local hospitals -- nine by ground and one by air ambulance. A total of 14 ambulances were used to aid patients following the riot.

#DonovanIC [final] Unified Command with @CACorrections has been terminated and all units are available. A big thank you to our local agencies at this incident. @SDFD @chulavistaFD @mercyambulance @sandiegocounty pic.twitter.com/iNWmwcUAYy — CAL FIRE/SAN DIEGO COUNTY FIRE (@CALFIRESANDIEGO) February 15, 2019

Walker said the inmate who was airlifted suffered a major head injury. Three other patients were considered "major trauma" injuries, and the rest suffered minor injuries. Those patients were all taken to hospitals via ground ambulances. He could not elaborate on their conditions.

According to the CDRC, some prison officers were residually affected by the release of pepper spray and were treated at the prison. No other injuries to officers were reported.

In the aftermath, investigators found several makeshift weapons at the scene. Bracamonte said he didn't have details on what those weapons were, and what materials had been used to make them.

Immediately following the riot, the prison was placed on lockdown. SkyRanger 7 spotted inmates outside the facility sitting on the ground in handcuffs. A line of officers was opposite them.

One person wearing a neck brace was loaded in the back of an ambulance staged right outside the door leading to the prison yard before the ambulance took off.

Bracamonte said the investigation is in its beginning stages and detectives are trying to determine the cause of the riot and whether it was premeditated. At the news briefing, he said nothing indicated the riot had been racially motivated by any one group at the facility.

Incident at Donovan State Prison. We’ve heard several rounds of apparent gunfire. We’ve seen several ambulances roll out. Also, an helicopter air ambulance has landed. #nbc7 Working to get official information. pic.twitter.com/lQClyyDnI5 — Artie Ojeda (@ArtieNBCSD) February 15, 2019

Bracamonte said the riot happened while inmates in Unit A were having time outside, in the recreation yard. He said rec time is held daily in that area from 8:30 a.m. to 11:30 a.m.

When the riot started, the inmates were under normal “staff observation,” Bracamonte said.

The CDRD captain said inmates in Unit A are considered “medium custody inmates,” classified by the CDRD as a “level 3” in terms of security. He said, typically, a “level 3” inmate wouldn’t be prone to this type of disturbance.

Bracamonte said investigators are looking into any tension or history in Unit A that may have led to the riot.

As the investigation continues, Bracamonte said the facility will be “modified,” but will not be on lockdown. He said this means “inmate movement is limited,” so investigators can continue to work at the prison and begin interviewing witnesses.

Donovan Correctional Facility is a state prison located just north of the Otay Mesa Point of Entry and on the outskirts of the Otay Open Space Preserve. Bracamonte said the facility currently houses 640 inmates.

And yet another ambulance leaves Donovan State Prison. We’ve noticed white vans are following the ambulances. There are likely guards in those follow up vans. #nbc7 pic.twitter.com/h7xPzuGmFO — Artie Ojeda (@ArtieNBCSD) February 15, 2019

The prison made headlines in June 2018 when a federal lawsuit accused several guards of running a Mafia-style criminal gang at the prison. The lawsuit said prisoners were beaten and retaliated against guards who were allegedly part of the so-called "Green Wall" gang.

In August 2016, four correctional officers were attacked by an inmate at Donovan state prison. The ordeal began when inmate Charles Morgan spit on a correctional officer and hit him in the face. Three more officers were struck by the inmate in that incident.

During Friday's response to the prison, an NBC 7 news crew heard about a half-dozen loud bangs coming from the prison but noted a San Diego County Sheriff's Department shooting range was located near the facility.

Bracamonte confirmed no guns were fired inside the prison during the riot and the gunfire heard by crews was from the nearby firing range.