The Department of Corrections says it's investigating what happened after an inmate was found dead inside his cell at the Stillwater prison.

At 2:43 a.m. on Dec. 1, prison staff found inmate David John Ojeda unresponsive, according to an emailed statement from Minnesota Department of Corrections (DOC) spokesman Aaron Swanum.

The prison staff performed lifesaving measures while emergency medical responders were called to the facility. The responders determined Ojeda had died, Swanum said. No further details have been released about the circumstances or cause of death.

Ojeda, 43, was sentenced in February after being convicted of criminal sexual conduct with a child younger than 16. He was serving a 25-year sentence.

In June, another inmate at Stillwater, Dalmario Smith, was found unresponsive and died. Investigators suspected that Smith may have ingested synthetic drugs before his death.