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Stephen Lowe disappeared from his Portsmouth Dr workplace about 10am on Friday.
His black BMW car was found by a member of the public in the Catlins Conservation Park area on Tuesday morning.
Senior Sergeant Cynthia Fairley said on Wednesday evening that police would like to hear from "Mike and Talia" who had been tramping in the area over the weekend.
The pair may be from the Dunedin area and were asked to contact Snr Sgt Fairley on 021 191 5318.
Police and 31 LandSAR volunteers from the Catlins, Dunedin and Clutha areas continued the search on Wednesday, which included the use of three dogs and an aerial search by helicopter.
The aerial search was limited to due to dense native bush in the area.
Police said there was significant land and tracks covered around the McLean Falls area. Swift water searchers from Dunedin would be included on Thursday.
The search was suspended at 6pm on Wednesday for the safety of all those involved.
Police also want to hear from anyone who was in the Owaka or Tautuku areas over the weekend and who may have seen Mr Lowe's car.
Detective Sergeant Nik Leigh said Mr Lowe's family had been informed and spent time in the search area on Tuesday.
''We are supporting as best we can," he said.
Anyone with information could also contact Balclutha police on (03) 418-0203.