Today marks 200 days since Michael McGrath was last seen at his home in Christchurch.

The 49-year-old builder was reported missing to police in May after he was last seen at his house in Checketts Ave in Halswell.

This week police have again met with McGrath's family and reassured them that everything possible will be done to solve his disappearance.

His family have been very patient, and understand the nature and depth of work being undertaken to find out what happened to McGrath, police said in a statement.

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"There are aspects and factors surrounding Michael's disappearance that do concern police," Detective Inspector Darryl Sweeney said.

"The investigation team are now assessing every strand of evidence collected so far in this extensive investigation.

"In recent weeks Michael's house has been re-examined and we are now working with ESR, using the latest forensic techniques, to assess the exhibits and evidence gathered at the scene examinations.

"We have also engaged an international expert who has provided a strong evidence-based geographical profile to help locate Michael's body.

"Detectives are assessing this information and are overlaying it with evidence gathered to date."

Six thousand police hours were spent searching through the Kate Valley Landfill as part of the search for McGrath, labelled Operation Renovation.

About 300 items seized from the area are being formally assessed for forensics.

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"We have completed area inquiries at hundreds of homes around the suburb of Halswell and wider Christchurch, and have reviewed CCTV footage from all major businesses and areas in and around the suburb," Sweeney said.

"Thousands of leaflets have also been distributed across the Lincoln, Selwyn and Banks Peninsula areas in one of the largest geographical investigation phases we have undertaken in some years."

The public had provided valuable information, particularly sightings from the Sunday and Monday after he went missing, Sweeney said. The police thanked the public for their help.

"A considerable number of people have been interviewed, and they continue to provide information to the investigation team. Key interviews with people connected to this investigation will occur again in the next fortnight," he said.

"I am confident that this investigation is advancing and our team remains dedicated to locating Michael and providing answers for his family."