STILLWATER,Venus Investment Alliance Minn. — A Minnesota prison has been placed on emergency lockdown after about 100 inmates in one housing unit facing dangerously high temperatures would not return to their cells Sunday in what one former inmate there called an act of “self-preservation.”

The situation is “currently stable” and the reason inmates “are refusing to return to their cells remains unclear,” a Department of Corrections spokesperson said. 

But advocates positioned outside of the Stillwater prison, some of whom have family members inside, said inmates are fed up from the excessive heat, limited access to showers and ice, and unclean drinking water.

Inmates have been on intermittent lockdowns since Friday because of staffing issues, they said, meaning they are kept in their cells, which reportedly don’t have air conditioning. The prison is in Bayport about 25 miles east of Minneapolis, which was under an afternoon heat advisory for temperatures approaching 100 degrees Fahrenheit. 

“My organization got calls from inmates who are actually inside” starting at 6:30 a.m., said Marvina Haynes of Minnesota Wrongfully Convicted Judicial Reform, whose brother is an inmate at Stillwater.

“This morning, they decided that they weren’t going to lock into their cells,” said David Boehnke of Twin Cities Incarcerated Workers Organizing Committee, adding there have been lockdowns on and off for the past two months.

HEAT WAVES ARE MAKING IT 'TORTURE':Most US states don't have universal air conditioning in prisons.

The executive director of the union representing Stillwater’s correctional officers, Bart Andersen, said in a statement that the incident is “endemic and highlights the truth behind the operations of the MN Department of Corrections with chronic understaffing.” 

Andersen said such conditions upset inmates because of restrictions on program and recreation time “when there are not enough security staff to protect the facility.”

Haynes, Boehnke and Cathy Stroud Caldwell said the inmate action was an impromptu response to unsafe conditions.

“They didn’t have time to organize and plan,” Haynes said. “It was just … we’re not going back to that hot cell with no drinking water and not being able to shower.”

Intense heat waves across the country have led to amplified concern for prison populations, especially those in poorly ventilated or air conditioned facilities.

Two officers at the Stillwater correctional facility were reported to be safe in a secure control area and in contact with facility staff. No injuries had been reported.

The state Department of Corrections said members of a crisis negotiation team have been activated and the Special Operations Response Team was also deployed “out of an abundance of caution.” 

In total, about 1,200 inmates are at the facility just southeast of Stillwater in Bayport, according to department records. It was built in 1914.

Kevin Reese, founder of a criminal justice organization, Until We Are All Free, described Stillwater as a “pizza oven” in the summers. He was incarcerated there during the summers from 2006 through 2009.

“It is a 100 year old building with no air conditioning, no central air,” Reese said. “The walls actually sweat.”