You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Detective Sergeant Derek Shaw said the objective of the morning was met, albeit unsuccessfully.
"We covered off the set area based on the information we had, but unfortunately without finding the location of Chris.
"It’s sort of a successful failure. It’s another part of the jigsaw we can probably tick off."
Volunteers searched an area near the Manuherikia River where the last signal from Mr Bates’ cellphone was picked up, on February 12, and beside an area where an empty cigarette packet of the brand of cigarettes Mr Bates smoked was later found.
Mr Shaw said he hoped for "a break from the public" with new information.
"Our opportunities are getting more limited.
"We’re keeping an open mind as to why we haven’t found him but we’re gravely concerned for his wellbeing."
Mr Shaw said there would be a debrief and review process following the latest phase of the inquiry.