Six Vermont inmates have tested positive for COVID-19 after returning to the state from a Mississippi prison, the Vermont Department of Corrections announced Thursday.

The prisoners were transported by van to Rutland's Marble Valley Regional Correctional Facility on July 28 and were immediately quarantined and tested for the novel coronavirus, the department said. They remain in medical isolation.

According to the department's website, 219 of Vermont's 1,405 prisoners are currently housed at Tallahatchie County Correctional Facility, a private prison owned by CoreCivic and located in Tutwiler, Miss. Another Vermont inmate who lived in the same unit as three of the six infected prisoners and who remains in Mississippi also tested positive for the coronavirus earlier this week, the department said. It has called on Tallahatchie to test all Vermont prisoners remaining at the facility.

In a written statement, interim Corrections Commissioner Jim Baker noted that his department had mitigated previous outbreaks in Vermont facilities.

“What we know is our efforts have effectively eliminated the presence of COVID inside Vermont facilities, and if the virus enters it will be from outside our walls,” Baker said. “What we hope is that the Vermont model of mitigation works in this situation."

Prior to the arrival of the Mississippi inmates, 48 in-state prisoners had tested positive for COVID-19 in recent months, as had 20 Corrections staff members.