German police investigating the disappearance of Madeleine McCann have found a sealed-off cellar after excavating an allotment site.
Witnesses said that they had watched as the BKA, the German federal investigation bureau, lifted off a cement block covering the basement during the first day of digging at the site just outside Hannover.
After discovering the cellar, officers led in a sniffer dog, which barked as it entered.
"The sniffer dogs were barking quite a lot in the morning," one person who was present said.
Authorities began searching the site on Tuesday in connection with the disappearance of Madeleine.
German police believe that she is dead.
Last month, Christian Brueckner was named as the prime suspect in what German authorities are treating as a murder investigation.
The convicted paedophile was living in the Algarve in Portugal when Madeleine went missing in May 2007.
German police claim they have evidence linking him to the case.
By Tuesday evening, police had dug a two-metre hole at the centre of the allotment, with forensic tents next to it. The dig continued yesterday from 7am in a different area of the garden.
Cement and other heavy duty materials were seen being removed from the site in the town of Seelze. It was reported police had brought in metal detectors and ground-penetrating radar equipment.
Wolfgang Kossack (73) who owns the plot next door, told reporters that a man with two dogs lived in the run-down shed on the site in 2007, the same year Madeleine disappeared.
"I can't tell you if it was the same guy. What I can tell you is that he was there with two dogs. One was small and brown, the other one was large and black," he said.
"He was there for between eight and nine months around about 2007. I went on holiday one July and when I came back, he was gone."
He and his wife had a few "uncomfortable situations" with the man, whose dogs defecated in their garden and whose car, a cream-coloured Volkswagen camper van, "stank of diesel".
"At first he apologised but became increasingly aggressive," Mr Kossack said.
That description fits 43-year-old Brueckner, who had two dogs while living in Hannover.
While in Portugal, he drove a white and yellow VW Westfalia camper.
Residents living next to the five allotment plots said they were "disused and overgrown" and had been "for years".
Mr Kossack said: "It was a ruin. He tried to do up the roof and insulate it and he seemed to sleep there from time to time."
One man, who lives across the road from the plot, said: "The people there were just normal folks who didn't live there. They just came here to get away from the city. I can't remember anything about the people who were there, but there was a Volkswagen camper that would turn up now and again. It was white and red."
Brueckner was found guilty of two crimes during his time in Hannover.
In 2010, he was charged with falsifying documents and ordered to pay a fine. Three years later, he was convicted of theft. He did not serve a prison sentence.
While in Hannover, Brueckner lived in a high-rise apartment block in Linden.
One neighbour said a man and woman who fitted the description of Brueckner and his girlfriend had lived in a bottom-floor flat.
While admitting that she did not know them, she said "there was something strange about them, they didn't fit in".