Police have serious concerns for Nigel Peterson, 33, who is missing in the Rotorua area. He was last seen on Otonga Road on the afternoon of Friday 17 November.

The father of missing autistic man has revealed the "gut wrenching" disappearance of his son three-weeks ago was sparked by a ruptured boiler.

Chris Peterson said his son, Nigel Peterson, was cared for 24/7 at a supported living facility in Rotorua where he was happy, settled and well looked after.

"Unfortunately on that Friday morning the hot water cylinder ruptured and flooded the house and the boys had to shift out."

NZ POLICE Nigel Peterson has been missing for more than three weeks.

He said that Nigel got wind of the move and "he just panicked".

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"He thought this was the end of his world, he felt his world would crash around him."

Peterson said his son took off with a carer in pursuit, though she was unable to keep up with him and in the confusion did not have a mobile phone with her.

He said she returned for her phone, came back "and he'd gone".

In a further twist, Peterson said Nigel was later spotted at the new Hemo Gorge roundabout.

"That's bamboozled him," he said.

He believed Nigel would have seen the arrows pointing out of town and simply followed them.

"That's what an autistic boy will do."

Nigel was sighted at Waipa and the road to Taupo but in a further misfortune, police were searching town.

Search efforts were hit with more bad luck on Thursday, December 7, when police and search team personnel to had been looking for Nigel were diverted to Rotorua's Blue Lake to find a missing Bristish tourist.

"We've been one step behind him all the way. It's been so frustrating," Peterson said.

He said sightings occurred on State Highway 38 and last Sunday around Lake Rerewhakaaitu.

Peterson said that despite the three-week period his son has been missing, he was hopeful he was alive and would be found.

"We haven't given up on him," he said.

"He's fit and strong, able to walk and he's tough. He's got a lot of stoicism in his make up, he's got a toughness in there. He'll just keep walking."

Peterson said one huge factor hampering the search is people's unwillingness to engage with someone with disabilities, or someone they may incorrectly believe is drunk.

"That's where we've fallen over. People have met and seen him. He just doesn't know how to ask for help."

Peterson said the pattern of sightings, then no sightings had been "gut wrenching".

"You can't get crueller than this. Hope, then no hope. It's the cruellest thing."

Peterson urged anyone who believes they may have seen Nigel to contact Rotorua Police on 07 349 9554, or 111 for an immediate sighting.

He also asked motorists who may have travelled in the area to think whether they may have seen a man walking in a manner that may have struck them as odd, and to check dashcam footage if available.