Forensic officers,sniffer dogs and an excavator were seen at a garden near the former home of a key suspect in the British girl's disappearance.
Christian Bruckner was one of 600 people of interest investigated by police after Madeleine's disappearance in 2007,but officers now admit they never followed him up.
The statement came as it emerged he could walk free from prison if the European Court of Justice overturns his conviction for raping an American pensioner.
German police have repeatedly refused to share details with McCann's family of the evidence they have until they are able to charge their prime suspect.
The Braunschweig state prosecutor said police needed more information about where Christian Brueckner had lived so police can search for Madeleine's body.
Shortly after Madeleine McCann went missing,the prime suspect moved to a village where he lived with German foster carers and helped track down runaway teens.
There has been a long-running war of words between British and Portuguese authorities about the handling of the McCann case,particularly over the woeful preservation of the crime scene and Madeleine's parents being incorrectly named as suspects.
Authorities have not released the suspect's name,but he has been widely identified by the German media as Christian Brueckner,aged 43.
It is tempting to hope that this week's"major breakthrough"might signal some kind of end,both to the anguish of the McCanns and to the world's fascination with it.
The British girl who disappeared in Portugal in 2007 is assumed to be dead and an imprisoned German child abuser is the murder suspect,a prosecutor says.
UK Police did not name the man but said he is 43 and was in and around the resort area on the Algarve coast at the time McCann disappeared in 2007.