THUNDER BAY, Ont. -- Ontario's police watchdog says a man who died in his cell last summer received "substandard" care from Thunder Bay police, but there are no grounds to lay criminal charges against any officers.

The Special Investigations Unit says police were called to a church on Aug. 2, 2014 and found an unconscious man who turned out to be seriously intoxicated.

The SIU says paramedics checked him out before police took him to the station, where he was placed in a cell.

The agency says the 44-year-old man was found unresponsive in the early morning hours of Aug. 3 and paramedics pronounced him dead at the scene.

SIU director Tony Loparco says that while the officers were right to arrest him "for his own safety," they should have taken him to hospital after he complained of breathing difficulties.

And he says the man was left unattended in his cell for more than five hours, despite police policies that require jailers to make physical checks of any prisoners every half hour.

Loparco says an autopsy found the cause of death to be ketoacidosis complicating diabetes mellitus, chronic alcoholism and septicemia.

It's unclear whether getting the man to hospital would have saved his life, he says.

"A tragic series of missteps by all the officers involved in the man's custody conspired against him that day," Loparco said in a statement.

"While I am satisfied on the evidence that the care the man received from the police was substandard, I am not satisfied on balance that the care of any one officer was markedly so in the circumstances. For the foregoing reasons, the grounds in this case fall short of proceeding with criminal charges."