A massive sinkhole opened up on a main street in the Canadian capital of Ottawa causing a gas leak and evacuations of nearby businesses and office blocks.

The incident took place on the corner of Rideau Street and Sussex Drive next to a shopping mall and near several important government buildings.

City officials do yet know what caused the sinkhole and refuse to speculate where the nearby construction of the new light rail system.

Mayor Jim Watson told reporters: "It's premature at this point to make the connection to LRT, although that could very well be the possibility.

"If you look back in the last year, there was probably a major sinkhole in every city, at least once a week somewhere in North America or around the world that's on the nightly news, and we're one more."

Nobody was hurt or reported missing as a result of the sinkhole while many witnesses recall the strong smell of gas and the loss of calls.

Witness Tom Herlihy was walking along Rideau street when he heard and smelt the gas leak: "A high-pressure natural gas line escaping is very distinct, it's a high-pressure whistle.

"You could smell it in the area immediately, and people were running away from it, you could tell something was amiss."

On getting a better look from an upper storey of a nearby hotel, Mr Herlihy told CBC: "I caught the hole expanding and the car falling in and the gas just roiling the water, causing the dirt underneath the street to erode and collapse. And it's really deep."

The city's emergency and protective services general manager, Anthony Di Monte, said that after the water main break and gas leak, both were shut off.

He added that emergency workers are stabilising the area while attempting to mitigate damage, but have yet to begin investigating the cause.

"We don't have the basic information to formulate a plan yet for the next few days," said Di Monte.

The sinkhole comes ahead of the "Three Amigos" summit in Ottawa between Mexican President Enrique Pena Nieto, U.S. President Barack Obama and Canadian Prime Minister Justin Trudeau on 29 June.

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