The head of the company whose Christmas party ended in a death says staff are shocked it is being treated as a homicide.

Darren Perry Grace, 40, died following the party on board the Quest 2 on Friday night during a function for the Pacific Hygiene company.

Police today said preliminary findings from a post mortem examination revealed Mr Grace was asphyxiated and they were now treating his death as a homicide.

Mr Grace was on board the yacht as a guest of a Pacific Hygiene employee.

Pacific Hygiene managing director Rodney Downs said few partygoers, other than the person who invited him, knew Mr Grace.

"There's no blame involved with any of our team or even with the staff member who invited the guest. We're just trying to support each other at this stage and also Mr Grace's family," he told Radio New Zealand.

"Obviously staff are in shock and it's just a tragedy, especially this time of year. It's been a pretty full-on year, it's the last thing we all needed but we just want to express our condolences to the family and his friends and to support them in any way we can."

Mr Downs said staff had seen Mr Grace get into difficulties shortly after dinner. An Auckland Hospital trauma nurse who was on board as a guest performed CPR but was unable to save him.

"We did our best, we had great people on board to do the CPR and I don't think we could have done any more and St John Ambulance have said the same thing.

" It was difficult, there wasn't much room up on the deck there where he was."

Mr Downs said staff and the company were now co-operating with police as they tried to find out exactly what happened.

Mr Grace's funeral will be held on Wednesday.