Next Wednesday marks the fourth anniversary of the day the pair disappeared, leaving few clues other than the wreck of a car at the bottom of a cliff.
On March 13, 2015, 11-year-old Mike was picked up from Southland's James Hargest College by Mr Beckenridge.
Several days later, the wreckage of Mr Beckenridge's dark-blue Volkswagen Touareg was found near Curio Bay in the Catlins.
There were no bodies inside, and there have been no confirmed sightings of the pair since March 17, 2015.
Police would not be interviewed about the case, but in a statement Detective Senior Sergeant Stuart Harvey said the investigation remained active and police were
''not in a position to provide details in regard of the lines of inquiry being undertaken.
''During the course of the investigation a variety of information has been received from the public and this information has been thoroughly assessed and investigated by the inquiry team.''
Mr Beckenridge, Mike and Mike's mother Fiona Lu, lived at Queenstown's Lake Hayes Estate until 2014, when Ms Lu met her present partner, Peter Russell, and moved into his Invercargill home.
Former Queenstown neighbours of the family declined to comment when contacted this week, but both said they had been contacted by a production company making a documentary about the case.
The company, named by one of them as Greenstone TV, did not respond to a request for comment.
