Police have searched through 2500 tonnes of rubbish at the Kate Valley Landfill in the search for missing builder Michael McGrath.

The 49-year-old left his home on Checketts Ave in the Christchurch suburb of Halswell on May 21 and hasn't been seen since.

Canterbury police field crime manager Detective Inspector Darryl Sweeney said police had completed their search of the dump and would now focus on the assessment and forensic examination of "items of interest" recovered there.

But police are keeping quiet on what they found.

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The investigation team had been at the dump since the June 15, searching with the help of New Zealand Army staff.

Police search a rubbish tip in Christchurch as part of Operation Renovation, the search for Michael McGrath. Photo / Supplied
Police search a rubbish tip in Christchurch as part of Operation Renovation, the search for Michael McGrath. Photo / Supplied

"It has been tough work in the midst of winter for all involved; police officers, including leaders of all ranks, took turns to uncover evidence for this case," Sweeney said.

"We are determined to obtain answers for Michael's family and this is an example of the detail that the police will go to, to establish the truth."

A fortnight ago police said they had identified key geographical areas of interest in the greater Christchurch region as they looked for McGrath.

After consulting with an international expert in locating evidence specialist search teams began looking at those specific areas to find evidence relating to the builder's disappearance.