An inmate at the California State Prison, Los Angeles County in Lancaster has tested positive for the COVID-19 virus, becoming the first state prisoner known to have contracted the illness, officials announced Sunday.

The prisoner has been in isolation since Thursday, when he reported to prison staff that he was not feeling well, according to the California Department of Corrections and Rehabilitation.

“He was tested for COVID-19 on March 20 and the positive test result was received March 22,” the agency said in a written statement. “The patient is in stable condition and is being treated on-site.”

Movement at the facility was “restricted” while officials investigated who the infected inmate may have had contact with, according to the CDCR. Anyone deemed to be at-risk will be quarantined.

“Any incarcerated individual who shows symptoms for COVID-19 will be tested for COVID-19 as appropriate,” the statement said.

While no other inmates have come down with the novel coronavirus in the California state prison system, two staff members at the California Institution for Men in Chino have been infected, as well as two staff members at California State Prison, Sacramento and one at Folsom State Prison.