Transportation Safety Board investigators are focused on a length of broken rail as the likely cause of Tuesday’s fiery train derailment in central Saskatchewan, an all-too-familiar incident that has raised questions about the state of repair of Canada’s rail lines.

Twenty-six cars of a CN freight train derailed near the village of Clair. Two DOT-111 tanker cars carrying liquid petroleum products then exploded into flames, forcing the evacuation of nearby homes.

"There were some signs of distress and wheels going over a piece of rail that was broken already," Rob Johnston, head of TSB rail investigations in the agency's central region, told CBC News.

"Pieces of the rail head are worn, they're battered. There's some indications this had broken and there's some indication wheels had run over the rails. So [it’s] quite possibly the point where it likely occurred."

The TSB said it's now reviewing CN’s inspection and maintenance records along the stretch of track as part of its investigation.

Video shows nearby loose rail spikes

CBC News has obtained a cellphone video shot by a local resident showing a stretch of track near the crash site, which appears to show loose and missing rail spikes.

The unknown residents in the footage, whose faces are not shown, comment that a number of railway spikes are easily removed and so loose they appear not to be fastening the rail down to the wooden railway ties.

The TSB has been told of the video and said it is reviewing the condition of the track in the area.

TSB reports dating back several years reveal that broken steel rails, shifting rail beds and derailments stemming from "track failure" are nothing new in Canada.

Eight TSB crash reports in the past five years blame problems with the track that were either missed by inadequate inspections or were neglected and not fixed in time:

  • In April 2013, 17 cars loaded with potash derailed near Provost, Alta., when a CP train derailed. TSB finding: Track known to be vulnerable, not fixed.

  • In January 2012, 17 cars fell of a bridge near Fabyan, Alta., as CN train derailed. TSB finding: Inspections found broken, lifting screws, which were a contributing risk factor.

  • In April 2012, 10 empty tank cars derailed colliding with an adjacent CP locomotive. TSB finding: Track defect.

  • In July 2011, a CN train derailed 11 intermodal cars, tearing up a long stretch of track. TSB finding: History of defective ties, track alignment and wheel problems.

  • In December 2011, an AMT commuter train in Montreal derailed a single coach car. TSB finding: Substandard track inspections and maintenance.

  • In October 2011, a CN freight train near Alix Junction, Alta., derailed 7 cars including dangerous goods. TSB finding: Snapped old rail not detected by company inspections.

  • In August 2010 near Airdrie, Alta., a CP train derailed 32 cars including dangerous goods. TSB finding: Rail breaks due to "undetected rail defects" despite testing shortly before.

  • In August 2010, 17 cars of a CN freight train derailed near Clova, Que. TSB finding: Track shifted after repair work, undetected by inspections.

This list of crash investigation findings doesn't include the scores of minor derailments and accidents reported to the TSB caused by broken rails that did not result in a full-blown investigation.

CN investing 'billions'

"Doing the inspection is one thing,” Paul-Emile Soucy of Edmundston, N.B., told CBC News after an incident near his farmhouse in January of this year. "Doing the repairs is something else."

Soucy said CN had already identified the stretch of track along the Napagodan Subdivision as being in need of major upgrades when a freight train derailed 500 metres from his home last winter.

"It's a rail that broke, beneath the crossing, and there was two cars that flipped over," he recalled of the Jan. 26 incident. 

"The ties are all rotten. They don't replace them quick enough or fast enough. And they were supposed to do them last year or the year before."

He said he spoke to a CN inspection crew last year who were travelling along the rails spray-painting red markings on rotted-out rail ties, and he was told the entire length of track needed to be replaced.

"You can inspect the tire on your car and say it's worn out. But if don't do nothing about it, you end up having a flat tire or an accident. So they do do the inspection on the track, but they did not replace the ties."

CN Rail issued a statement Friday saying the stretch of track passing Soucy’s farm is slated for a multimillion-dollar upgrade with replacement of 44,000 rail ties to commence next week.

"CN invests significantly in its rail infrastructure to maintain safe operations and has a continuing program to upgrade its Napadogan Subdivision in New Brunswick," CN’s Mark Hallman wrote in an email to CBC News.

"In 2014, CN plans to invest approximately $2.25 billion in capital programs across its North American network, of which more than $1 billion is directly targeted toward maintaining the safety and integrity of the network, particularly track infrastructure," Hallman wrote.