The Transportation Safety Board says it may have found the cause of last week's coal train derailment in B.C.'s Fraser Canyon.

Board spokesman Dan Holbrook said investigators have found what appears to be a defective piece of rail and have sent the metal to a lab for analysis.

Holbrook also said there was no indication of the problem during an inspection just a month ago.

A dozen cars of a Canadian Pacific coal train went off the CN track near Lytton last Monday.

It was the first of two accidents in the area last week. On Friday, nine CN Rail cars carrying grain went off the CN track about 10 kilometres south of Lytton.

The derailed cars fell onto the CP line on the embankment below, closing that track as well.

There were no injuries in either accident.

Meanwhile, rail traffic is moving again on the repaired rail lines and CN said crews are working to clear the backlog.

With files from the Canadian Press