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Mystery Tunnel 20150224

A map showing where an underground tunnel was found in Toronto is shown in this undated police handout photo. Toronto police there's nothing to suggest a criminal element is involved in a mysterious underground chamber found near a Pan Am Games venue in the north end of the city. THE CANADIAN PRESS/HO - Toronto Police Service

Inside Toronto's 'mystery tunnel'

A mysterious tunnel with reinforced walls, electric lighting and a generator has police and Torontonians scratching their heads. It was found in January near the location of the Rexall Centre, a venue for the upcoming Pan Am Games.

More on the mystery tunnel: Toronto cop's tweet goes viral | Cops appeal to public for help