The investigation into missing Invercargill boy Mike Zhao-Beckenridge and his stepfather John Beckenridge will not be closed, despite police referring the case to the coroner.
A forensic examination of the car linked to the pair's disappearance has found no sign of human remains.
The vehicle was pulled from the sea near Curio Bay earlier this month after it had been submerged in rough seas for a couple of months.
Southland area commander Inspector Kelvin Lloyd yesterday said police remained ''ever hopeful'', but the treacherous seas and the condition the vehicle came out in had been ''major frustrations'' in the search.
''It's essentially left of us with a chassis, a motor and three wheels - and that's all that's been left of the vehicle,'' he said.