The prison system continues to get hit by the pandemic. According to a report from The Denver Post, at least 138 inmates at Colorado’s largest prison, Sterling Correctional Facility, have tested positive for Covid-19.

The Colorado Department of Corrections tested 473 inmates Wednesday and 255 results had been returned as of noon Friday. Along with the positive diagnoses, 104 were negative, meanwhile 12 results were inconclusive and one result was unsatisfactory. The Colorado Department of Corrections started the expansive testing after eight inmates tested positive.

“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,” Department of Corrections Executive Director Dean Williams said in a news release. “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.”

The facility has been on lockdown since April 14 to prevent the spread of the coronavirus. That means that inmates eat their meals in the cells and can only leave their cells to shower or use the restroom. Meanwhile, staff and inmates are required to wear masks and inmates on the east side of the prison are getting their temperature checked twice a day, according to the department.