MONTREAL (AFP) - A sophisticated tunnel has been discovered near a major sporting venue and a university in Toronto, reports said Monday, with Canada on edge over the threat of possible extremist attacks.

A municipal worker was walking through woods near York University and the Rexall Centre last month when he spotted a piece of corrugated metal on the ground, lifted it up and found a passageway, the public broadcaster CBC said.

The tunnel was about seven metres long and 2.5 metres tall and was lit by an electric generator. The walls and ceilings had been reinforced and tools had been left inside.

Toronto is hosting the Pan American Games in July and the Rexall Centre is one of the venues. The facility also hosts major tennis events.

National security officials have been alerted but there was no immediate suggestion the tunnel posed a threat, CBC said.

Authorities have now filled it in but police were tight-lipped about what its purpose might have been. CBC said authorities had ruled out the possibility of it being a drug lab.

Canadian authorities are on alert following two Islamist-influenced attacks last year that resulted in the deaths of two unarmed soldiers in Ottawa and Montreal.

And in a recent video the Al-Qaeda-linked Shebab insurgent group threatened Canada's massive West Edmonton Mall, along with a mall in the United States and a major shopping district in Britain.