Inmates used a smuggled cellphone to create their own "Mannequin Challenge" video inside a California state prison.

The video was filmed inside the Richard J. Donovan Correctional Facility, Terry Thornton, with the California Department of Corrections and Rehabilitation, confirmed Thursday, according to KNSD.

"Inmates are not supposed to have cellphones, that is considered contraband in California state prisons," Thornton told KGTV. "Cellphone possession in prison is illegal."

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The one-minute clip features about a dozen inmates. It starts with one seated on the toilet then pans to others sitting and standing around the cell. It shows two inmates holding a shirt over another with fists clenched in a mock fight. It was uploaded to YouTube Nov. 13.

Authorities are investigating the incident, including how the inmates got cellphones, which are not allowed in the prison.

"An inmate caught with an illegal cellphone can lose up to 90 days of good time credit," Thornton told the San Diego Tribune. "There could be other sanctions as well."