RCMP say the death of ex-city police officer at Headingley Correctional Centre Tuesday morning was due to natural causes.
No other information is to be provided.
Dow, 58, was found unconscious at about 10:30 a.m. Attempts to resuscitate him were not successful.
Foul play is not suspected.
Dow was serving a 16-month jail term for sexual assault. He was sentenced in September after being convicted of sexually assaulting 11 young women he persuaded to model for his off-duty photography business.
He was scheduled to be released this summer.
The offences occurred between 2001 and 2005. Thirteen more women stepped forward in January 2007 to make complaints against him. In total, there were allegedly 17 women and five girls under age 18 who were victimized. Police said the victims ranged in age between 15 and 24.
Dow was a Winnipeg police officer for 19 years. He retired in February 2007.