An inmate was found unresponsive in his cell at the Barton jail last Wednesday morning, said a spokesman for the ministry that oversees the jail.
Paramedics were called to the jail and the man was pronounced dead, the ministry spokesman said.
The cause of his death is unknown.
If the coroner determines drug use was a factor, the man's death may be added to an inquest announced in August 2015 into the deaths of five men who died of drug-related overdoses at the jail.
Though it's been a year and a half since that announcement, it's unknown when the inquest will happen, according to Cheryl Mahyr, a spokeswoman at the chief coroner's office.
Mahyr would not disclose how many deaths are now included in the inquest, or who the supervising coroner will be.
The ministry of correctional services declined to comment further on the most recent death while it's under investigation.
"Should the Coroner's death investigation determine that the inmate's death was anything other than natural causes, a mandatory inquest will be held," said Andrew Morrison, the spokesman for Ministry of Community Safety and Correctional Services.