A man found dead in a Manukau police station cell this morning was checked on throughout the night and the cause of death remains unknown, police say.
The 64-year-old man was arrested about 8pm yesterday and spent the night alone in the Manukau police station custody unit.
He was routinely checked throughout the night and was found unresponsive at 5.40am today, police said.
Police staff commenced CPR immediately and called an ambulance, but the man was pronounced dead when paramedics arrived.
An investigation into the man's death has been launched and the incident has been referred to the Independent Police Conduct Authority.
Police said they were awaiting the results of a post-mortem examination before the cause of death could be established.
"This incident is a tragedy and we extend our deepest sympathies to his family," Counties Manukau District Commander Superintendent John Tims said.
"We are doing everything we can to support the family at this difficult time."
The man's name has not yet been released.