New details are emerging about the death of an inmate at Hawke's Bay Prison on Friday.

NZME understands he was 30-year-old Gisborne man Kolby Heta, and that he's being farewelled at a tangi in Gisborne today.

Police and the Department of Corrections have confirmed they're investigating a death.

Detective Senior Sergeant Martin James said a post-mortem was carried out on Saturday, but investigators are now focusing on the circumstances of the death.

Acting prison director Nephi Hall confirmed the prison was locked down after the death, in line with normal practice.