Police are searching an allotment in Hanover in connection with their investigation into a 43-year-old man suspected over the disappearance of Madeleine McCann, German prosecutors have told the BBC.
Christian B was revealed last month as the main suspect in the investigation.
He is a sex offender currently in prison in Germany.
British girl Madeleine was three years old when she went missing while on holiday in Portugal in 2007.
She disappeared from an apartment in Praia da Luz on the evening of 3 May 2007, while her parents were with friends at a nearby tapas bar.
Her disappearance sparked a huge police hunt across much of Europe.
Last month, the Metropolitan Police said the case remained a "missing persons" investigation. However, German investigators have classed it as a murder inquiry.