South Auckland police say they regularly checked on a man being held overnight in the cells, who was found dead this morning.
They say a 64-year-old man who was arrested about 8pm last night was found unresponsive about 5.40am this morning.
Police said he had been alone in his cell all night and was routinely checked on.
They were awaiting results from a post mortem carried out today to determine the cause of death.
The matter has been referred to the Independent Police Conduct Authority.