Police believe "something more sinister" may have happened to a Korean man missing since his car crashed off State Highway 1.
Fifteen searchers scoured bush and rivers about 2km north of Kaiwaka on Saturday in an unsuccessful search for any trace of 28-year-old Hyung Jun Cho, who hasbeen missing since his abandoned car was found damaged down a bank last December.
His father, Seung Wook Cho, made the trip to Northland on Friday and was at the search briefing on Saturday with an interpreter, hoping his son would be found.
It is the third thorough search police have made since Hyung Jun Cho disappeared - and the third time they have found no trace of him.
This has led them to consider other possibilities.
Detective Sergeant John Clayton was part of the team that covered 20ha of bush during the latest search.
He said some smaller areas would be covered this week using a specialist search dog from Whangarei.
"The possibilities now surrounding his disappearance become more sinister. If he was picked up by someone driving on the highway it must have been one of the very first cars to go past after he crashed," Mr Clayton said. "He's made it up on to the road and someone knows something."
He urged people with information to come forward.
There was no blood or any other clue inside the wrecked car to suggest Mr Cho had been seriously injured.
A scene-of-crime officer had searched Mr Cho's car, and police would this week consider whether it should be forensically examined by scientists from Environmental Science and Research.
Mr Clayton said he went through the extensive police file with Mr Cho's father and explained through the interpreter what had been done to try to find his son, who lived and worked in Ruakaka.
Once Mr Cho's white four-door Mitsubishi was found, police started a search, using torches as night fell to scour nearby farmland and bush.
The police team, including a sniffer dog and handler, and about 16 search and rescue volunteers battled rough weather before calling off the search.
When dawn broke, members of the Korean communities from Ruakaka and Whangarei continued the roadside search from the crash scene to Whangarei, looking for clues.
