More than half of the inmates who were tested for the coronavirus at the state’s largest prison have tested positive, the Colorado Department of Corrections said Friday.

Of the 255 test results that have been finalized, 138 inmates at the Sterling Correctional Facility tested positive, according to a news release. Twelve tests came back with inconclusive results and one was unsatisfactory.

Earlier this week, the CDOC and Colorado’s Department of Public Health and Environment tested 473 symptomatic and asymptomatic inmates from several units in the east side of the facility, where inmates have either tested positive or were previously quarantined. Previously, eight inmates had tested positive.

Authorities are still waiting for the results from the remaining 218 tests.

“Given the insidious nature of this virus we had suspected that despite seeing a relatively low number of inmates with symptoms, the number of positives was potentially much higher,” said Dean Williams, CDOC executive director. “That is exactly why we conducted this large scale testing, so that we can continue to isolate, monitor and treat any inmates who were positive and try to mitigate the spread to others inside the facility.”

Several protocols have been implemented to curb the spread of the virus among staff and inmates, including increased cleaning by staff. All inmates and employees are required to wear face coverings and inmates on the east side of the prison have their temperature checked twice a day.

Since April 14, all prisoners have been required to stay inside their cells unless they need to shower or use the bathroom, the release stated. Meals and medication are delivered to their cells.

No deaths at the prison have been reported.