Forty steel bolts that were meant to keep the deck of the new, $100-million Nipigon River Bridge securely fastened down have been sent to two independent labs in Ontario for testing and analysis as provincial officials continue to search for what caused the bridge to buckle.

Still, the hope is to have the bridge that crosses the Nipigon River re-opened to two lanes of traffic by the end of February, restoring the link along the TransCanada Highway between eastern and western Canada, Ontario Transportation Minister Steven Del Duca told reporters in a conference call Tuesday morning.

The bridge has been reduced to one lane of traffic since Jan. 10 when it suddenly broke apart – with one section of it lifting 60 centimetres. It had only been opened for a couple of months when it failed.

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It is on the only route through Canada, and is regularly used by commercial truck drivers. Drivers now face delays of between five and 10 minutes as a pace car guides the traffic across at a speed of about 25 kilometres an hour.

Exactly what caused last week's break in the bridge remains a mystery. The Ministry of Transportation does not know how much all this will cost or who is responsible.

"We are taking into account at this point a number of possible factors and we haven't ruled anything out," said Mr. Del Duca, who stressed that the design of the bridge met the Canadian Highway Bridge Design Code and was built to withstand winds of more than 100 km/h and temperatures below -40 C.

One possible factor being looked at is the role of the 40 bolts, which are 22 millimetres in diameter and 150 mm in length, and secured the deck of one lane to beams. The bolts were manufactured by R.J. Watson, a reputable firm, in New York State.

Mr. Del Duca said the bolts are being examined by the National Research Council of Canada and the University of Western Ontario.

The bolts will undergo a visual and chemical analysis. Experts will also look at their "mechanical properties," a "determination of the nature of the failure," and a comparison of how they stack up to the design specifications, according to Mr. Del Duca, who read a statement describing the operation.

Officials are also studying the tension on cables that help support the bridge. This is Ontario's first "cable-stayed bridge" – the weight of the deck is supported by overhead cables.

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Gerry Chaput, assistant deputy minister, provincial highways management division of the Ministry of Transportation, said that because the buckling was at one end of the bridge, there was some concern the cables were too tight.

He said this issue has been reviewed, and that the tension on the cables was appropriate for the loads and other factors affecting the bridge. However, he said, they continue to "look at numerous factors as to what caused the failure."

Queen's University civil engineering professor Mark Green said that officials will want to find out through the analysis of the bolts whether they had adequate strength for the job they were doing; some grades of steel are much stronger than others and are better at lower temperatures.

In addition, he said a visual examination of the bolts will show whether they were pulled apart or sheared-off, which will help in analyzing the combination of factors that may have led to the bridge buckling.

He said the encouraging news is that the bridge is intact.

"So it's just really determining … is there something with these bolts that it wasn't exactly as expected. Were they loaded in some way that wasn't exactly understood?" he said.

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Progressive Conservative transportation critic Michael Harris said that testing materials for this bridge should not be taking place after the fact.

"It's too late then," he said. "Where was the oversight and the proper engineering testing to ensure quality materials were being used and that the construction was being done as per plan, if the plan was even proper in the first place."