Police dog units are hoping to pick up the trail of a frail 63-year-old man, who went missing from a Dunedin hospital last week.

Gordon Mclean, 63, known as Gordy, has not been seen since leaving Wakari Hospital on Thursday afternoon.

Extensive searches had already been carried out in the Waikari, Frasers Gully, Halfway Bush and Helensburgh areas, leaving police with serious concerns over Mr Mclean's welfare, Sergeant Richard Panting said on Monday.

Southern DHB's medical director for mental health, addictions and intellectual disability, Brad Strong, says Mr McLean had been in a non-secure rehabilitation facility.

There would be a review of the disappearance, he said.

"Our focus at this stage is on working with the police," Dr Strong said.

"However, we will be fully reviewing the circumstances around his departure and care in light of these events."

Sgt Panting urged residents in the area to check their properties again for signs of Mr Mclean.

"Even if you find something you don't believe would be of interest, please still take the time to contact us," he said.

When he was last seen, Mr Mclean was wearing a dark-coloured polar fleece and trousers, a red-coloured polo shirt, brown slippers and a black sleeveless puffer jacket.

He is described as 152cm tall, thin and "very frail".

About 60 volunteers joined the search for Mr Mclean over the weekend.