A derailment and explosion in a CN Rail marshalling yard in Prince George 18 months ago is being blamed on a lack of training among management staff and rail cars that were too heavy.

A report released by the Transportation Safety Board Tuesday found that managers operating a remote control switching system when the explosion occurred on Aug. 4, 2007, weren't properly trained for the duties they were performing.

"Although considered qualified from a regulatory perspective for their respective duties, the management employees . . . were inadequately trained and had no experience switching long, heavy cuts of cars on this particular piece of track," said board investigator Peter Hickli.

The accident involved a CN supervisor losing control over a 53-car remote controlled train, which struck another train pulling cars loaded with gasoline. The crash caused a derailment, explosion and fire.

"The collision occurred when the excessive tonnage of the 53 cars and the descending track gradient . . . combined to exceed the braking capacity of the switching locomotives," Hickli said.

No one was hurt but 172,000 litres of gasoline and diesel spilled, most of which burned in the fire.

Kelli Svendsen, spokeswoman for CN, said the company has been working diligently since the derailment to improve the safety of its railroad and employees.

"In 2008, CN had a 30 per cent reduction in overall accidents in Canada than in 2007 and we're seeing this trend continue in 2009," she said.

Svendsen denied the board's finding that the employees were inadequately trained for their duties at the time of the derailment.

"In CN's view, the employees were experienced, they were well-rested, and they were trained to perform the duties that they were performing. The TSB did note that the employees were considered qualified from a regulatory perspective."

When pressed on whether the employees could be qualified for the duties they were performing from a regulatory standpoint while still lacking the experience to perform those duties seamlessly, Svendsen reiterated the company's belief that experience was not a factor in the derailment.

The board also found that a risk assessment conducted immediately prior to the accident was inadequate to identify the hazards and mitigate the risks of switching long, heavy cuts of cars on the pull-back track's descending grade.

While the board report made no formal recommendations in its report, it said "the practice of temporarily assigning management employees to do the work of experienced operating employees may increase the risk of accidents."

The safety board went on to say that the lack of a formal quality assurance program to establish consistency in risk analyses increases the likelihood that the controls identified and implemented may not be sufficient to address the risks.