A newly constructed bridge in northern Ontario has heaved apart, indefinitely closing the Trans-Canada highway — the only road connecting Eastern and Western Canada.

The Nipigon River Bridge has been closed for "an indefinite time due to mechanical issues," according to the Ontario Provincial Police. The bridge remains open to pedestrian traffic.

Steven Del Duca, minister of transportation for Ontario, said in a statement late Sunday the ministry "will do everything they can do to restore the bridge quickly, while also making sure that the safety of the travelling public remains of paramount importance."

The west side of the bridge has pulled away from the abutment connecting it to the river bank's edge, lifting up about 60 centimetres.

As a result, police have shut down Highways 11 and 17 at the bridge, which is located about 100 kilometres northeast of Thunder Bay, Ont.

Nipigon bridge-workers

Crews worked late Sunday night on the Nipigon River Bridge, with the Ministry of Transportation pledging to safely restore the bridge as soon as possible. (Jeff Walters/CBC)

The estimated duration of the closure is "uncertain" with police noting it could be "possibly days."

"It's not just us. It's all of Canada that has a problem right now," Nipigon Mayor Richard Harvey told CBC News. "This is the one place in Canada where there is only one road, one bridge across the country."

Engineers are on site trying to determine what caused the bridge to fail, but "the reality is nobody really knows what happened," said Harvey.

He said transport traffic in the area has backed up and the township is opening up community centres to give anyone stranded a place to stay.

Map of Nipigon River Bridge

Police have shut down Highways 11 and 17 at the Nipigon River Bridge, which is located about 100 kilometres northeast of Thunder Bay, Ont. (Google Maps)

Harvey added that police quickly started to stop people heading out on the Trans-Canada Highway at larger Ontario centres like Sault Ste. Marie, Thunder Bay and Terrace Bay, telling them to turn back or use an alternate route through the U.S.

'Big gust of wind'

Ashley Littlefield, who lives in nearby Dorion, Ont., witnessed the failure Sunday afternoon as she was driving with her husband.

Nipigon

Dozens of transports are lined up at the Husky Truck stop in Nipigon, with the other two truck stops in town just as packed. (Jeff Walters/CBC)

"As we turned [onto the highway], we saw the whole bridge — a kind of big gust of wind came underneath it and blew it up and then it came back down," she said, adding it shifted by about half a metre.

"We watched two pickup trucks come flying over. … They didn't see us, didn't hear my horn honking, and they flew over and smashed their front ends down on the cement."

Littlefield said her husband got out to stop traffic before police arrived about 30 minutes later.

The Ontario municipality of Greenstone, located along Highway 11 northeast of Nipigon, has declared a state of emergency as a result of the closure.

The Nipigon River Bridge is in the midst of a twinning project – a $106-million rebuilding that will see the old structure replaced with two identical, two-lane expanses.

Ontario heralded the opening of the westbound portion of new Nipigon River Bridge – the province's first cable-stayed bridge – in late November. Work on the eastbound lanes continues, and is slated for completion in 2017.

hi-nipigon-river-bridge-852

A concept drawing shows the Nipigon River Bridge, which is expected to be completed in 2017.