Police yesterday took soil samples from Woodland, which have been cleared in search of Claudia Lawrence.
Officers were focusing on a tennis court-sized area where they were seen taking up soil for testing.
The day before, they had cut down small trees.
Officers have spent 11 days exploring fish ponds and forest land in Sand Hutton, where Claudia, 35, lived in York.
He declined to say what sparked the new search.
Even her mother, June 78, has not been notified.
Claudia disappeared in 2009 while on her way to work at York University.
No one has been charged with suspected murder.