The sister of an autistic man who's been missing since Friday is imploring the public to keep an eye out for him.

Michelle Peterson's brother Nigel was last seen at around 3pm on Otonga Road, heading towards Old Taupo Road, in Rotorua.

He went missing when he had to move out of his home temporarily.

'He has a home in Rotorua with flatmates and caregivers, which he loves,” says Michelle. 'But the water cylinder flooded and they had to move to another site for a week. He got confused and upset about that, thinking he wouldn't be allowed back. So he ran away on Friday, and now he's lost.”

Someone initially spotted him running away, and managed to keep up with him. But they turned back to get help, and by the time they returned to bring him back, Nigel was gone.

Nigel has a bank card, and normally goes to the dairy quite often. But it hasn't been used since Friday, raising concerns he's somewhere he can't access a shop.

'He's very vulnerable, because he doesn't like to talk to strangers. He can be unsure of people – he can't tell if someone is good or bad, so he tends to avoid people,” says Michelle.

'He has certain anxiety traits that people should notice, though, like wringing his hands or talking to himself. We're asking people to keep an eye out if someone looks out of place.”

Michelle and her friends and family have been using social media and pamphlets to get the word out in the hope someone will recognise him and be able to help. Since it's possible he got a ride with someone at some point, he could be anywhere in the central North Island.

'Our only hope at the moment is the public.”

If you think you may have seen Nigel since 3pm on Friday, or have information which could help police to locate him, please call 111 or ring Rotorua Police on 07 349 9139 and quote file number 171117/2007.