Murder-suicide likely - police

Southland police searching for a missing boy at Curio Bay have revealed they believe he has been a victim of a murder-suicide.

Mike Zhao-Beckenridge, 11, disappeared on 13 March with his step-father John Beckenridge, in breach of a custody order.

After investigating for nearly a month, police say all the evidence points to a tragic murder-suicide involving John Beckenridge driving his stepson off a cliff into a rocky Catlins cove.

Tyre tracks found at the top of the cliff at Blue Cod Bay stop at least a metre from the edge, and the man's luxury Volkswagen was found 90 metres into the cove, showing it was driven at speed.

Police have also confirmed that before the car went over, Mr Beckenridge sent a series of text messages from Curio Bay to Mike's mother, his neighbour, friends and solicitor containing messages with the tone of a goodbye. There have been no sightings of the pair since.

Detective Sergeant Mark McCloy said police divers could not see bodies inside the car, but he wants it out as soon as possible.

He said options included trying to float the vehicle to deeper water, but they have to wait for calm seas to make the attempt.

"We've looked at cranes but that's no longer on the table, there are various different options around trying to float the vehicle into deeper water using airbags... etcetera on top of the cliffs to try and extract the vehicle."

Detectives were still intending to try to drag the wrecked SUV out of Blue Cod Bay but said they would only do so when the water is calm.

Previously, police had said that, though unlikely, they had not ruled out the possibility the pair had left the country.