The prime suspect in the Madeleine McCann case was hired by an allottee who was being searched by police in Germany, a man who claims a neighborly conspiracy.
The owner of the allotment told the BBC that the suspect Christian B had arrived there the year Madeleine went missing.
German prosecutors have said that the search on site near Hannover is related to the investigation of Christian B, a jailed sex offender.
Work began on the site on Monday and is expected to continue until Wednesday.
Medellin was three years old when she went on vacation with her family in Portugal 13 years ago.
She disappeared from an apartment in Priya da Luz on the evening of 3 May 2007 while her parents were with friends at a nearby tapas bar. It hunted a huge police force in most parts of Europe.
The man, who was discovered by his neighbor, told the BBC that Christian B had rented the plot for a few months in the year that Medell disappeared.
The man said that Christian B came in the spring or summer of 2007 and told him that he wanted to dig up a small hut that stands on a concrete base in a garden with a small basement.
The neighbor went on leave in July 2007. When he returned in August, he said, the structure was removed and he never saw the suspect again.
Christian B was revealed as the prime suspect in the case in June, as German and UK police appealed afresh for help.
The surnames of suspects do not usually appear in Germany for confidentiality reasons.
The 43-year-old is believed to have been in the area where Madeleine was last seen while on vacation in Algarve, Portugal.
Police said he regularly lived in Elgarve between 1995 and 2007 and worked in the area, including catering, but also dabbled in the hotel and drugs businesses.
German prosecutors have previously said they have evidence convincing them that Christian B has killed Madeleine, but not strong enough to take him to court.
Last month, the Metropolitan Police said the case remained a “missing person” investigation in Britain because there was no “definitive evidence” of whether Medellin was alive.
However, German investigators have said that they believe Madeleine is dead.
Following the latest police appeal, Madeleine’s parents, Kate and Gerry McCann, said: “We will never give up hope of getting Medellin alive, but whatever the outcome, we should know that we need to find peace.” “