LISBON, Portugal —  Police investigating the disappearance of a 4-year-old British girl searched an area of remote scrubland in southern Portugal on Friday, but said they found nothing.

Officials sealed off the area after receiving an anonymous tip Madeleine McCann might be buried there, police spokesman Olegario Sousa told The Associated Press by telephone.

"We found nothing," Sousa said.

Police with sniffer dogs cordoned off the area just after dawn, Sousa said, and left several hours later. The site was about nine miles from the hotel where the girl vanished while on vacation with her family.

Earlier this week, the Dutch paper De Telegraaf said it had given police an anonymous letter it received with a map of the area.

Police say they have followed up dozens of leads, included reports of sightings of Madeleine by the public, but none has yielded results.

Madeleine disappeared on May 3 from a hotel in Praia da Luz, a resort town in Portugal's Algarve region. Her parents left her and her 2-year-old twin siblings alone in their hotel room while they dined at a nearby restaurant.

The couple has since launched an international campaign to find the girl, enlisting the aid of celebrities such as soccer star David Beckham and J.K. Rowling, author of the Harry Potter books.

Kate and Gerry McCann have also traveled to Spain, Germany, the Netherlands and Morocco to plead for help in finding their daughter. They fear Madeleine may have been taken out of Portugal, but say they have no plans to return to Britain without her.