An out of district police investigator has been brought into Hamilton to investigate the unexplained death of a man while in police custody.

Emergency services were called to a Dinsdale home shortly before midnight last night where a 26-year-old man, who was trespassed from his ex-girlfriend's property in June, had shown up.

When he arrived at the house an altercation between him and a 23-year-old man at the property developed, Waikato District Commander Superintendent Win van der Velde said.

When police arrived at the home the two men were still fighting.


The 26-year-old was placed in handcuffs, Mr van der Velde said.

"[But] after a very short period of time, as they were making arrangements for the intruder to be transported back to the Hamilton station our staff became concerned about the man's wellbeing and asked a nurse present at the dwelling to check the man while calling for ambulance staff to attend."

The man was unable to be revived and was pronounced dead at the scene.

His death is being described as unexplained and sudden.

The other man involved in the fight was taken to Waikato Hospital for medical observation.

A senior, out of district investigator has also been appointed to head the police inquiry "to ensure the independence of the investigation", Mr van der Velde said.

The Independent Police Conduct Authority has also been notified and the man's death has been reported to the coroner.