Portuguese police said the operation in the Lagos area in the country’s tourist-friendly south, where Maddie disappeared in May 2007, would run from Monday until Friday.
Portugal’s Judicial Police said it was carrying out “a wide range of investigations, namely search warrants” in the Lagos council area, which contains the Praia da Luz holiday town where Maddie was last seen.
Any evidence found would be sent to German federal police, the Portuguese agency said in a statement on its website.
CNN Portugal reported the searches would be carried out between Praia da Luz and one of the houses where Breuckner lived around the time the girl disappeared at the age of three.
It reported the new phase of the investigation was aiming to find possible remains of Madeleine.
Braunschweig prosecutors told Reuters “criminal procedural measures” were taking place involving the Federal Criminal Police Office (BKA) and Portuguese police.
London’s Metropolitan Police also acknowledged the searches.
“We are aware of the searches being carried by the BKA in Portugal as part of their investigation into the disappearance of Madeleine McCann,” a spokesperson said in a statement sent to 9news.com.au.
“The MPS is not present at the search but will support our international colleagues where necessary.”
Madeleine disappeared from her family’s holiday apartment on May 3 2007, days before her fourth birthday.
Despite an investigation spanning more than 18 years, no charges against a suspect have ever been laid.
Brueckner has not been charged in the McCann case, in which he is under investigation on suspicion of murder.
He spent many years in Portugal, including in Praia da Luz around the time of Madeleine’s disappearance there in 2007. He has denied any involvement in her disappearance.
He is currently serving a seven-year prison sentence after being convicted in 2019 by the Braunschweig court for the rape of a 72-year-old American woman in Portugal in 2005.
