A 40-YEAR-OLD prisoner has died overnight at Alice Springs Correctional Centre.

A statement from Northern Territory Police said circumstances surrounding the death were being investigated and a brief would be prepared for the coroner.

Police media said the man was indigenous but would not release any other details.

It is the second Northern Territory death in custody in a month.

On May 21, 59-year-old Kwementyaye Langdon was found dead on the floor of his cell at the Darwin watch house.

He had been placed their just three hours for drinking in a dry zone.

Police had used the controversial paperless arrest laws, which allow them to people up without issuing a charge or infringement notice.

Langdon was an Aboriginal man believed to have moved to Darwin from Yuendumu.

All deaths in custody trigger a mandatory coronial investigation.