Mystery surrounds the disappearance of two Taranaki men whose cars have been located but who have otherwise vanished without a trace.

Karl Roberts, 31, has not been seen since August 1. Roberts lost control of his green Subaru Impreza while driving along Uruti Rd and crashed down a bank before coming to rest near a stream.

Roberts' sandshoes were found stuck in mud on the other side of the stream, about three kilometres from his car.

supplied Karl Roberts' car was found down a bank on Uruti Rd on August 1, but he hasn't been seen since.

Meanwhile, Thomas Milsom, 41, hasn't been seen since September 29. His car was found at the beach end of Epiha Rd, Motunui, north of Waitara, on Monday, October 2.

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* Police conduct an extensive search and rescue operation for missing man

* Family of missing Taranaki man continue to search rugged bush

Detective Sergeant Gerard Bouterey said it was routine for the CIB to be involved in cases of missing people.

Supplied Police are looking for any information or sightings of Thomas Milsom, or his car which has a distinctive back. Milsom hasn't been seen since September 29, but his car was found on Epiha Road, north of Waitara on October 2.

"Generally if someone is reported missing and they are not found within three days then the file will go to the CIB simply because they are the investigators," Bouterey said.

"The CIB gets involved in any missing person if they are not located within three days, or earlier if there is suspicious circumstances."

Police carried out an extensive search of the North Taranaki coastline during the weekend but didn't find any signs of Milsom, who Bouterey described as a loner who stuck to a routine.

"We don't believe that there's anything sinister in his disappearance but it's certainly out of character for him."

Detective Senior Sergeant Brent Matuku said missing persons files were regularly reviewed and police remained in contact with Roberts' family.

"We are satisfied that we have done all of the possible inquiries that we can at this stage," Matuku said.

There was nothing to indicate Roberts was dead and he was still deemed to be a missing person, he said.

Grant Roberts, Karl's father, said family and friends continued to search despite knowing there was only a slim chance their son was still alive.

"That's the thing. It's an unknown but it's not looking very likely, but there's always hope, I suppose," he said.

"There has been no further answers after finding the shoes, really."

Grant said there were still areas that had not been searched and they were just waiting for the weather to clear before heading out into the rugged bush to continue looking.

"It's just a matter of picking on places where we can fill in the gaps really, a few of the locals are keen to do more but it just revolves around the weather really.

"We are just waiting for the weather to dry out a little bit and I think next week we'll have a bit more of a look, not far from the vehicle to see if we can pick up any more clues."

Grant said the continued rain had been frustrating.

"It's worse when you can't get out there and search in some ways."

Police want to hear from anyone who has information about either of the missing men.