Investigation underway for missing Christchurch builder Michael Craig McGrath

Michael McGrath, 49, was last seen at his Checketts Ave home in the suburb of Halswell on May 21. Photo / Supplied

The out-of-character disappearance of missing Christchurch builder Michael Craig McGrath has police, neighbours, and locals worried.

McGrath, 49, was last seen at his Checketts Ave home in the suburb of Halswell on May 21.

A large police investigation is underway to find him.

Police started knocking his neighbours' doors last Thursday.

On Friday, they cordoned off his well-kempt red brick property where he lived alone.

Checketts Ave house of missing Christchurch man Michael McGrath. Photo / Kurt Bayer

Today, it remains taped off, with a large blue police tent in the front yard. The house curtains are pulled shut.

White boiler-suited officers have been seen coming and going from the property. A large police mobile base truck is parked out front.

Halogen lights are in the driveway and locals say there has been a lot of police activity over the last four days.

His brother Simon says while there will "obviously going to be all sorts of theories" about the disappearance, the family is focussing on any sightings of him or his blue 1994 Subaru Legacy station wagon.

Police were also interested in sightings of McGrath's 1994 Subaru Legacy. Photo / Supplied

In a Facebook plea for information, Simon said: "Very unlike him to go walking - has never done so before and he has been in good spirits."

Detective Inspector Darryl Sweeney, who is leading the investigation, said police "have concerns for his welfare".

It remains a missing persons investigation, police say.

Missing person posters have been placed around the area.

One neighbour said police came to her last Thursday wanting to eliminate her silver car from their enquiries.

"It's really strange. It has us all worried," she said.

McGrath's blue station wagon was taken away from his property - just a few doors down from 'Black Widow' husband killer Helen Milner fatally-poisoned Phil Nisbet in May 2009 - at the weekend.

Now, Sweeney is appealing for sightings of the Subaru over the weekend of May 20-22 in the Halswell area.

Neighbours describe McGrath as a quiet man who rarely had visitors.

"We hardly see him," one neighbour said.

"My kids say 'hi' to him when he's out gardening and when he was out biking which he did a lot."

She said everyone was "really worried", especially at the mounting police activity.

A local shopkeeper said McGrath came in occasionally - but again said he was a very quiet, solitary figure.

She also had concerns for his welfare.

"It's just fingers crossed really," she said.

Anyone who has information about McGrath or has employed him in the last few weeks is asked to call Christchurch police on 03 363 7400 and cite file number 170523/6008.

Information can also be provided anonymously by calling Crimestoppers on 0800 555 111.