Agrizzly and her two cubs are dead after being struck by trains in separate incidents just west of Banff in the Rocky Mountains.

The sow was on the tracks when she and one ofher cubs were struck Monday morning, park officials said.The mother was killed immediately, but the cubsurvived, only to dielater that day of its injuries.

The second cub, a year old,returnedto the area on Tuesday and was struck by a different train.

Hungry bears are drawn to the tracksto eat thegrain leaked by aging rail cars.

"There's nothing more heart wrenching than to see 100 metres of track where a bear has been struck and ground into small pieces underneath a train," said Jim Pissot, executive director of Canmore-basedDefenders of Wildlife Canada.

The animals don't move even when a train whistle sounds, but in some cases they move when an engineer flashes lights, Pissot said.

Before the second cub was found dead, Ian Syme, chief warden for Banff National Park,argued that it would be inappropriate to intervene.

"I think the important thing to remember here is that these cubs are of an age that they can survive on their own, and our ultimate intent really is tomake surethat we don't remove a potential breeding female or male."

Leaking cars being repaired

Canadian Pacific Railway is investing $20 million to identify and repair 6,000 of its cars that are responsible for spilled grain.

Pissot said that work won't be completed for another five years.

Ed Greenberg, a spokesman for Canadian Pacific, said in October interview with CBC News that the railwayhas a truck with a grain vacuum on it that cleans the rails, and railway staff are trained to keep rail cars securely fastened and prevent spills.

"We do more than any other railway in North America when it comes to dealing with wildlife along our railway tracks," he said. "The fact is, grain isn't the issue. This is an issue of rapid land development and expansion of human activities."