Wisconsin corrections officials say they don’t know how three more inmates in the state’s prison system contracted the coronavirus. The Department of Corrections believes the first prisoner with a confirmed case of COVID-19 April 2 was exposed while on a trip outside the Columbia Correctional Institution. On Sunday, the DOC confirmed three additional cases in the system. The three inmates had not left the prisons recently, according to DOC spokeswoman Anna Neal. One of the three cases is at Columbia where three employees have also tested positive. The other two inmates with COVID-19 are at Oshkosh Correctional Institution. No employees there have tested positive, so it’s unclear how the virus could have gotten into the prison.