THUNDER BAY, Ont. - Ontario's police watchdog is investigating the death of a man who was being held at a police station in Thunder Bay.

The Special Investigations Unit says Thunder Bay police arrested the 44-year-old man, who was in violation of a court order, at 4:30 p.m on Saturday.

The SIU says the man was intoxicated at the time of arrest.

At about 3 a.m., police say they noticed the man in his cell was in some form of medical distress and an ambulance was called.

Emergency medical responders pronounced the man dead.

The SIU has assigned three investigators and two forensic investigators to probe the circumstances of the death.