A 48-year-old inmate at Moose Lake prison collapsed and died in the shower Sunday morning after going into cardiac arrest.

Correctional officers found the man unresponsive around 9:45 a.m. and used an automatic external defibrillator (AED) until paramedics arrived, authorities said. The man died at the scene.

A preliminary investigation indicates that the man had complained of heartburn to fellow inmates before he entered the shower and collapsed.

Although the medium-security facility is at the epicenter of Minnesota's first outbreak behind bars, officials say the man had not reported experiencing COVID-19 symptoms and was not known to have had direct contact with anyone infected.

"There's absolutely no evidence suggesting a connection at this point in time," said Corrections Commissioner Paul Schnell.

The state agency is withholding the man's identity pending notification of next of kin. His death remains under investigation.

Inmates gathered in the day room Sunday morning reported seeing a first responder enter the facility wearing a HAZMAT suit. The measure was likely a precaution, Schnell said, since paramedics knew the facility had been exposed to the virus.

In less than a week, seven inmates have tested positive for the respiratory disease and another 13 are presumed positive based on reported symptoms. Among employees at Moose Lake, one is isolated with a confirmed case and another is presumed to be based on symptoms.

Two confirmed cases have also emerged in correctional officers at Red Wing juvenile facility 156 miles south. Tests are pending at prisons in Stillwater and Lino Lakes.