British police investigating the disappearance of Madeleine McCann have found no evidence relating to her during searches of three areas of land close to where she went missing but "more activity has been agreed".
Officers have spent eight days investigating areas of interest in the Algarve resort of Praia da Luz, with Scotland Yard confirming tonight that more will be carried out "shortly".
Further requests are also being compiled and will be submitted to the Portuguese authorities.
It follows unconfirmed reports last week that Scotland Yard has been granted permission to question three suspects about the case.
After police declined to comment about the recent activity in the resort, tonight's s tatement from Scotland Yard said there was "still a substantial amount of work yet to be completed in the coming weeks and months".
"This recent work is part of ensuring that all lines of inquiry are progressed in a systematic manner and covers just the one hypothesis that she was killed and buried locally," the statement said.
"This is the same as would be done in the UK for a murder or high risk missing person inquiry."
It described the deployment to Portugal over the past couple of weeks as the "largest ever undertaken by UK police overseas in a case of this type", with a total of 645,000 square feet of land searched, including all utilities, drainage channels and derelict buildings.
Police said the decision to search the horseshoe-shaped piece of scrubland close to the Ocean Club resort where Madeleine went missing aged three in May 2007, along with the two other sites investigated today, was a specific result of the UK's investigation work to date.
The three areas were identified as places to be surveyed after 41 ground anomalies were identified by both aerial survey and ground analysis.
British officers, accompanied by their Portuguese counterparts, spent seven days carrying out a methodical search of the first site last week, with TV crews and press from around the world descending on the small resort as the new development in the lengthy investigation took place.
Specialist teams including forensics officers, sniffer dogs and officers using ground-penetrating radar equipment were used on the large site, with the two areas searched today being smaller and on the outskirts of the town.
As police prepared to search the two areas today, graffiti slurring the McCann family and describing British police as "stupid" was scrawled on a nearby wall overnight.
A spokesman for the McCanns said they declined to comment on the graffiti, which was written in large red letters in Portuguese.
The new operation in Portugal is only being carried out at the request of the British authorities after they submitted four international letters of request.
The Portuguese have also reopened their inquiry into Madeleine's disappearance but, while they are working with the UK force, they have refused to set up an official joint investigation.
The searches have seen Operation Grange police officers working alongside specialists from around the UK including Sussex Police and South Wales Police, along with the Portuguese Policia Judicial and Guarda Nacional Republicana.
Before leaving the third site in the grounds of a large rundown villa tonight , Portuguese and British officers could be seen shaking hands and kissing one another as they said their goodbyes.
The Met's Detective Chief Inspector Andy Redwood, the senior officer investigating the case, was seen among them before walking off the site with colleagues.
He shook his head when questioned by reporters but when asked if the searches were now concluded, he answered: "Finished for today."
Madeleine went missing from her holiday apartment on May 3 2007 as her parents Kate and Gerry dined at a nearby tapas restaurant with friends.
Last week the McCanns said they were "encouraged" by the progress made by police during their latest searches.
Writing on the Official Find Madeleine Campaign Facebook page, the couple said: "We are being kept updated on the ongoing work in Portugal and are encouraged by the progress.
"Thank you for continuing to stand by us and supporting our efforts to get Madeleine home."