Police have not been able to interview the father of a boy who drowned in a West Coast goldmine pond on Sunday.

Tayne Bowes, 9, drowned after his father's Toyota Hilux flipped upside down in the waist-deep pond near Hokitika.

His 8-year-old sister, Keira, survived after spending nearly two hours in water in the submerged vehicle.

Their father had taken them to the private Adair Rd goldmine, where he worked, to refuel a pump.

Police said on Monday that it was unclear how the vehicle came to roll into the pond or whether the children's father had been in it at the time.

Officers had hoped to interview the father yesterday to establish the events leading to the accident, but that has been postponed until today.

Investigators had completed their scene examination, but a spokeswoman said police still had a lot of inquiries to make.

"We're nowhere near being in a position to say whether charges will be laid. We're still finding out what happened," she said.

The children's parents, Mark and Katrina Bowes, released a statement yesterday saying they were "devastated and heartbroken" at the loss of their son.

"Tayne was a bright and inquisitive young boy who enjoyed playing rugby and loved his sister dearly," they said.

Keira had been discharged from Grey Base Hospital and was at home with her parents.

"The family now wishes to focus on Keira's recovery and trying to come to terms with their enormous grief," the statement said. "This is a stressful and difficult time for the family."

The parents said they appreciated the "incredible support" they had been given by their friends, family and the West Coast community.

Tayne's body was expected to be returned to his family yesterday after an autopsy.

The family will have a private funeral service this week.

- © Fairfax NZ News