A man whose son drowned after his car rolled into a pond on the West Coast last month has finally been interviewed by police.

Mark Bowes has been in Christchurch Hospital for treatment for a brain tumour since the incident that killed 9-year-old Tayne on August 12.

Mr Bowes ran 3km to call police after his vehicle rolled into the pond near Hokitika. His 8-year-old daughter Keira was rescued from the submerged ute by police officers.

A police spokeswoman said he was interviewed between bouts of chemotherapy.


The spokeswoman would not disclose what was discussed or how the investigation was progressing.

Family friend Barry Foster earlier this month revealed that Mr Bowes was diagnosed with a terminal malignant brain tumour after the incident.

He said Mr Bowes would have tried to save his son's life ``in one instant'' had he not been suffering with the tumour.

At the time of the incident, police said the siblings were in the vehicle with their father, who had gone to his worksite at a goldmine to refuel a pump being used to drain a pit.

The vehicle plunged over a bank and landed upside down in the water and Mr Bowes scrambled out in the dark and ran for help.

Police officers described the rescue as ``bittersweet'' for the family, finding one child alive and the other dead.