A Toronto and Region Conservation Authority (TRCA) employee reportedly found the tunnel while walking near the TRCA headquarters at 5 Shoreham Drive in January.
CBC News has learned that the tunnel, which has since been filled in by authorities, was large enough for a grown person to stand in, at around 2.5 metres deep and running about 7 metres in length underground. The tunnel had lights inside and was powered by a generator.
It is unclear what the tunnel might have been used for, but CBC News has learned that national security officials have been notified. Toronto Police will not comment on the tunnel, but are expected to hold a press conference Tuesday.
The Rexall Centre is set to be a tennis venue for this summer's Pan Am and Parapan Am Games. Authorities speaking on behalf of security for the Games, however, said there is no defined threat at this point, and that "the threat level, as per the federal government, remains at medium level."
Tennis Canada, which operates in the Rexall Centre, is aware of a police investigation and cooperating with it.
In an interview with CBC News, Ray Boisvert, the former assistant director of intelligence at CSIS, said the discovery raises some important questions. "First and foremost is the question around the context of the tunnel — where it is positioned? How deep was it? How accessible was it? And what sort of things could be sent through that tunnel, being people or material."
CBC news has learned that authorities have essentially ruled out the possibility that the tunnel was going to be used as a drug lab or marijuana grow operation. It likely took weeks if not longer to dig before being discovered. The earth excavated from the tunnel appears to have been removed from the site to help avoid detection.
Boisvert said that the tunnel’s proximity to the Rexall Centre, Canada’s national tennis centre and a host site for the Pan Am Games, could be a concern for those involved in security for the Games.
"I would think that they would want to have some level of assurance that this was not targeting the games or targeting any other facility around there," he said.
"I would want to be able to have some sense that we know what the purpose of that particular tunnel was and who was likely — if not who, precisely — was behind it."
No one has yet come forward to claim the tools and generator or offer any explanation for its existence. CBC news has confirmed employees at several area gas stations were asked if anyone had been filling up gas cans recently that may have been used to power the generator.
So far, no suspects have been identified.
If you have any information on this, or any other story you would like investigated, please contact CBC Toronto’s Investigative Unit: email@example.com and firstname.lastname@example.org