Police said they had received preliminary post mortem results into the death of Queenstown rafting guide Moana-Roa Haare, who was known as 'Chief'.
The 62-year-old collapsed and died on the shore of the Shotover River on Friday after his raft upturned on a section called the Toilet rapids.
Police said the preliminary findings suggested a 'medical event'.
The death has been referred to a Coroner.
Tributes have been paid from all around the world for the whitewater guide, who had been working for Queenstown Rafting since 1996.