STILLWATER, Minn. — A century-old Minnesota prison was placed on emergency lockdown on Sunday after approximately 100 inmates refused to return to their cells.

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According to the Minnesota Department of Corrections, the Minnesota Correctional Facility in Stillwater was placed under lockdown, WCCO-TV reported. Prison officials said in a news release that two correctional officers are safe in the facility’s secure control area. Other staff members have been removed from the common area of the prison unit that was taken over by inmates, according to the television station.

Emergency situation ‘resolved’

Update 12:20 a.m. EDT Sept. 4: The Minnesota Department of Corrections said the emergency situation at Minnesota Correctional Facility - Stillwater has been resolved, WCCO-TV reported. However, officials said the lockdown at the 109-year-old prison may remain in place until Tuesday.

DOC officials said the incident was “resolved without incident” and there were no injuries, the Star Tribune reported.

Spokesperson Andy Skoogman said the facility remained on lockdown status after nearly all prisoners returned to their cells around 3 p.m. Sunday.

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

Advocates outside the facility said that inmates were protesting excessive heat inside the prison, limited access to showers and ice, and unclean drinking water, according to The Associated Press.

In a statement from the AFSCME Council 5, a union that represents corrections officers in Minnesota, Executive Director Bart Andersen said the lockdown was a result of “chronic understaffing” at the prison, KMSP-TV reported.

“Today’s incident at MCF- Stillwater is endemic and highlights the truth behind the operations of the MN Department of Corrections with chronic understaffing leading to upset offenders due to the need to restrict programming and/or recreation time when there are not enough security staff to protect the facility,” Andersen said in the release. “Our union believes to our core that our correctional facilities cannot have transformational offender programming without sufficient facility security, we can and must have both.”

According to the prison’s website, the facility was built in 1914 and includes seven living units, along with a minimum-security unit outside its main perimeter.

There are currently 1,202 inmates housed at the prison, KMSP reported.

In 2018, a prison officer was killed at the hands of an inmate, according to WCCO. Joseph Gomm, 45, was beaten to death with a hammer by Edward Johnson, according to the television station.

Kevin Reese, founder of Until We Are All Free, a criminal justice organization, told the AP that Stillwater as a “pizza oven” in the summers. Reese did time at the prison during the summer from 2006 to 2009.

“It is a 100-year-old building with no air conditioning, no central air,” Reese told the news organization. “The walls actually sweat.”