A mentally ill former Marine died in a Rikers Island jail cell last month possibly due to temperatures that topped 100 degrees, reported the Associated Press on Wednesday.

Jerome Murdough, 56, was reportedly on anti-psychotic and anti-seizure medication, which could have made him more vulnerable to heat, according to the AP. His cell also reportedly did not have a small vent, and temperatures rose to at least 100 degrees due to malfunctioning equipment.

Murdough was brought to Rikers on February 14, and was locked alone in the cell at 10:30 p.m., city officials told the AP. Although he was supposed to be checked every 15 minutes (since he was in the mental observation unit), he was not found until 2:30 a.m., after he had already died.

“He basically baked to death,” one of the officials told the AP.

The medical examiner’s office told the AP that the autopsy was inconclusive and more tests were needed before an exact cause of death could be determined.

In a statement, DOC acting commissioner Mark Cranston said they are undergoing a "full investigation" into Murdough's death. Cranston acknowledged that a preliminary investigation indicated the temperature in Murdough's cell was "unusually high," and he said that the department had undertaken "remedial action" to make sure safe temperatures are maintained in the cells.

"I smell a cover-up ... The only thing I can think of, you murdered my brother," Murdough's sister, Chery Warner, told Eyewitness News. Warner and Murdough's mother, Alma Murdough, insisted he should was not violent, and never should have been in Rikers in the first place.

News of Murdough’s death came the same day that The New York Times published a review of internal Rikers reports that indicate an increase in violence among the mentally ill at the jail complex. Current and former mentally ill inmates at Rikers told the Times they had experienced violence from both the guards and their fellow inmates.