The police are not ruling out the possibility that a missing school boy and his stepfather have left the country.
Michael Zhao-Beckenridge, who is 11, was not at school when his mother went to pick him up on the 13th of March, and is believed to be with his stepfather John Beckenridge, who is in breach of a parenting order.
Police said there was very little chance the pair have left the country as no border alerts have arisen since they went missing almost a month ago.
They are working on recovering the wreckage of Mr Beckenridge's car from Curio Bay in the Catlins, which they hope will provide new clues.
Divers did not believe there were bodies inside the car.
The recovery of the car is being hindered by tidal conditions which are expected to worsen this week.