Writing on the Official Find Madeleine Campaign Facebook page Kate and Gerry McCann thanked their followers for the support they have received as officers carry out a methodical sweep of the land in the Algarve resort of Praia da Luz.
"We are being kept updated on the ongoing work in Portugal and are encouraged by the progress," the message said. "Thank you for continuing to stand by us and supporting our efforts to get Madeleine home." It was signed off "Gerry and Kate".
The McCanns, from Rothley in Leicestershire, have not travelled to Portugal where their daughter went missing in May 2007, aged three. Their message came after a further day of activity at the site, which saw British police accompanied by their Portuguese counterparts focusing on searching drains.
A five-man team was seen lifting three manhole covers and lowering a camera attached to a long pole down them, close to an area where ground-penetrating radar equipment was used yesterday.
Other officers spent the day working out of sight of the public's gaze and the lenses of the TV crews and press who spent the day watching from behind a police cordon which surrounds the site and is being guarded by armed officers day and night.
The operation has also seen forensics officers focusing their attention on a hole that was previously covered by undergrowth. But it is understood nothing of significance was discovered there, with bones found identified as those of animals.
The operation is likely to go into a second week after British police applied to the judiciary to spend an extra seven days there.
It was reported yesterday that Scotland Yard has been granted permission from the Portuguese authorities to question three suspects about the case.