GREEN BAY, Wis. (AP) — Fifty-seven people have tested positive for the coronavirus at the Green Bay Correctional Institution, according to state officials.

All of the prisoners who have tested positive are being isolated and anyone who was exposed is being quarantined, the Wisconsin Department of Corrections said. All inmates and staff at the prison are in the process of being tested for COVID-19.

“As we’ve all learned about COVID-19, due to asymptomatic cases, mass testing is the only way for us to identify all persons in our care infected and isolate them from the uninfected,” DOC Secretary Kevin Carr said.

Three staff members are among the 57 positive cases, the State Journal reported.

Corrections officials completed a mass testing of inmates and staff at each of its 37 prison facilities at the end of July and just nine people tested positive.

The only other major outbreak DOC has reported in a Wisconsin prison was at the Waupun Correctional Institution in May and early June, when there were 228 positive COVID-19 cases. among prisoners. All since recovered from the virus.