Manitoba's police watchdog is investigating the death of a 40-year-old man following his arrest early Wednesday morning in Winnipeg.

The Independent Investigations Unit says police say the man was arrested on drug offences and placed under observation at the central processing unit.

Police say he was in medical distress and unresponsive about two hours later and was taken to hospital where he was pronounced dead.

The unit says it will have no further comment since the investigation is ongoing.