A tragic chain of events that caused a fatal January train derailment in Whitby, Ontario, was sparked by a broken wheel, Neal Foot, senior vice-president of operations for Canadian Pacific Railway, said yesterday.

Pointing to a picture of a wheel that has most of its steel tread broken off, Mr. Foot said, "You can see very clearly what the cause of the accident was. What happened was that the wheel broke and fell between the rails as the tread deteriorated and the width of the wheel narrowed."

But the derailment of the CPR freight westbound from Montreal to Toronto at 7:41 p.m. on Jan. 14 turned into a tragedy when the last two cars of the 1