A hidden cellar has been found in the hunt for Madeleine McCann, it has been confirmed.

German police discovered the basement in the foundations of a building in Seelze, near Hannover, where kidnapping suspect Christian Brueckner allegedly lived in 2007.

Neighbours say the wooden shed was demolished in late 2007 or 2008 – months after Madeleine disappeared.

Investigators, accompanied by special search dogs, have been removing slabs of building materials in a two-day search of the vegetable garden.    

Wolfgang Kossack, 73, who owns the plot next to Brueckner’s former allotment, said Brueckner had lived off-grid at the site in 2007.  

He told MailOnline: ‘I remembered his face from the pictures in the news. And I remember his van and his dogs. I had completely forgotten about him up until then.

‘Christian Brueckner had the garden next to mine. He arrived in 2007 and left within a year. He told me that he was living off the grid, that he had not registered with the authorities – no one knew he was there.

‘He never did any gardening. He did not plant anything or try to grow anything. He just sat around drinking beer.

‘At the time there was a building on the garden. It was a small wooden structure with only one room to keep tools and other things but it had a kitchen.

‘The building was not really a house, you might call it a shed. But it had a cellar and underneath there would be foundations. This building was destroyed in 2008.’

German press reports on Tuesday claimed police had discovered a cellar underneath a long-demolished gazebo.

Brueckner, who is currently in jail in northern Germany, is suspected of killing Madeleine after she vanished from her Praia da Luz holiday apartment in May 2007.

Last month a former friend of Brueckner reportedly claimed the kidnap suspect told him he had a cellar at a different property which he wanted to line with metal sheets ‘like Josef Fritzl’s’.

Retired electrician Mr Kossack, who has used the allotments since 2006, said he remembered Brueckner took it over in 2007 because the allotments had only been handed out by the local authorities the year before.

Mr Kossack said Brueckner disappeared in 2008 and he never saw him again. The plot of land was originally owned by someone else before it was passed onto the convicted rapist.

‘Sometimes a young woman would be there with him,’ added Mr Kossack, ‘She seemed to be his girlfriend. He had two dogs – a big one and a small one – who were quite annoying. They would come into my garden to do their business.

‘I remember he called the small dog, Frau Muller [a German nickname for a housewife].’

Before Brueckner left, he apparently talked about his time outside of Germany.

‘Brueckner said he preferred southern Europe because he liked the warm weather and said he would go back there,’ his neighbour said. 

‘He did not say which country. He had a VW Transporter van and parked it next to the allotment and lived in the vehicle.

‘The van was registered in Hannover but Brueckner had not paid the tax on the vehicle.

‘I asked Bruecker what he did for a job. He said he was a car mechanic. I asked him why he didn’t repair his own van because it was always leaking diesel onto the ground. He said he would get around to it sometime.’ 

Mr Kossack added: ‘I feel so sorry for the parents of Madeleine McCann. I hope they can find out what happened to their daughter.’  

Up to 100 officers using small diggers and sniffer dogs have been continuing to excavate the vegetable garden.

A tent has been erected on the plot concealing the exact nature of the search, and a wide cordon with wire netting has set been up around the allotment.

Two small tents have been set up in a field opposite the main dig site, while a fleet of German police vehicles lined the side of the small country road while commuter traffic drove past.

An apartment block in Hannover has been identified as Brueckner’s last known address in the city, and German media report he may have lived on the allotment itself – possibly in his trailer.

German authorities have released few details about the allotment search, beyond confirming that it was part of the Madeleine investigation.

Get in touch with our news team by emailing us at webnews@metro.co.uk.

For more stories like this, check our news page.