"That was a decision that they were trying to make on the Thursday, so we'd obviously like him located as soon as possible,'' he said.
Police would not speculate on why Matthew had gone missing.
"There's no reason for why he's vanished and until we probably speak to him, we can't fill in the gaps either,'' Mr Membery said.
"We can't really speculate that he's just run off, or it could be part of his medical condition which has made him disoriented, but that's another speculation.''
Police were not considering foul play at the moment.
"It's hard to fathom why he's gone missing but I'm sure once we find him we'll be able to work that one out.''
Police had followed up some possible sightings without success. One sighting was at a local information centre and another was at his school.
"It's still within the Rotorua area, so we're hoping he's still around and members of the public will help us locate him so we can obviously get him treatment.''
Police said Matthew was of very slim build, about 1.65m tall with Chinese features. He has shoulder length, straight black hair and has light facial hair on his top lip.
He was last seen wearing a black fleece jacket, black trousers, a beige shirt, black shoes, and carrying a green file box.
