The desperate search for a teenage boy with non-verbal autism, missing in dense Victorian bushland, has entered its third day,

William Callaghan, 14, has been missing since Monday afternoon after being last seen on the summit of Mt Disappointment while hiking ahead of his family then becoming separated from them.

Temperatures have plummeted to freezing in the two nights since and William was only wearing blue trackpants and a hoodie.

“We’ve had people searching 24 hours for the last couple of days and a lot of people out in the field,” Senior Sergeant Greg Paul told Nine’s Today on Wednesday.

Crews have been different techniques to try and find William, including playing Thomas the Tank Engine over PA systems.

“We’re fairly confident we can have success. We’re thinking positive.,” Snr Sgt Paul said.

“There is a sense of urgency obviously but we are really hopeful we’ll get a successful day today.”

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Hundreds of people have been searching for the teen, who taps on his chest to communicate.

He went missing without food and water and could have covered a lot of distance, police said.

It is believed he could have tried to walk into a house for food or find a bed, and police have asked residents to check their outhouses.

AAP

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