Outdoor enthusiasts and farmers are being asked to keep an eye out for a police dog missing in the Mount Holdsworth area, west of Masterton.
The three-year-old German Shepherd, called Thames, went missing in the Totara Creek - Red Creek area on Sunday afternoon while taking part in a search and rescue exercise.
Thames was walking out of the area with his handler and other Wairarapa Search and Rescue squad members and civilian volunteers at the end of the annual day-long training exercise.
Teams stayed in the bush overnight to try to find him, after calling and searching main tracks and dense bush failed to turn up anything.
Senior Sergeant Mark Davidson said Thames' handler stayed overnight in the bush with others looking for the dog.
"That's what the handlers would do - they would want to be there to be part of the search for their working mate," Mr Davidson said.
"The bond, that affinity, that the handler has with his dog and the dog has with him is very strong, so the handler will be very, very upset.
"This handler, he won't be leaving the area until he has found his mate, I can tell you."
Police were hoping the sable-coloured dog, more used to tracking and finding people instead of being the subject of a search, was making his way down the mountain and following stream beds to safety.
Local farmers and others living near the Mt Holdsworth access roads have also been asked to keep an eye out for him.
Mr Davidson said Thames' disappearance was a nightmare as he was not only a loved workmate for his handler but also an expensive resource.
"We just can't afford to have them go missing. We're just putting as much resource and time into locating him as we possibly can, one being it's like losing any workmate," he said.
"The Wellington dog handlers are a big part of that so they're itching to get over there and give some assistance as well."
Mr Davidson said police were still hopeful Thames would be found.
Police said they had received numerous calls from members of the public who wanted to help find the missing dog.