CALGARY -- Conservation officers in Alberta aren't sure whether they have a serial poacher on their hands, but five grizzly bears have mysteriously died in the past three years, the latest one this week, and all not far from Jasper National Park.

Wildlife officials in Hinton, about 270 kilometres west of Edmonton, received a call Sunday from a driver who found a dead grizzly just south of the town.

The female bear, perhaps two or three years old, had been shot and left to rot.

Nine days earlier, a biologist who had been tracking grizzly bears in the province, called the same office with his discovery. The carcass of Mary, a seven-year-old female grizzly he had named and been following for four years, was located along a road south of Hinton. Mary's radio collar and ear-tag transmitter had been removed and dumped. Officials won't reveal the cause of death.

But Tony Brooks, a conservation officer with the fish and wildlife division of Sustainable Resource Development, said both bears were killed "within close proximity" of one another and both likely died some time between Sept. 15 and Sept. 20.

Mr. Brooks is baffled by the killings. His records are even more troubling.

Last year, a dead male grizzly was found southwest of Hinton. Mr. Brooks wouldn't disclose the cause of death or the state of the carcass. But the year before, he said, a mother and her cub were found shot and abandoned even farther south, near the community of Cadomin. All five cases are under investigation. Could the same person be responsible?

"I couldn't comment on that one. It would be speculation on my behalf," Mr. Brooks said. A connection is being considered, but these cases are notoriously hard to crack.

"That's why we're asking for public assistance in these matters and we're trying to emphasize that point," said Mr. Brooks, adding that tips can be made anonymously (1-800-642-3800) and could qualify for a reward.

Poachers can face up to two months in jail, a $5,000 fine or both if convicted under the provincial Wildlife Act.

The province said four grizzlies have been killed illegally each year for the past three years. In 2001, charges were laid in three cases.

Earlier this year, wildlife officials in Central Alberta found the carcass of a mature male grizzly along the Red Deer River. It had been shot and its head and paws had been removed. The parts were eventually recovered, but nobody has been charged.

Jim Mitchell, the conservation officer working the case, said poachers sometimes go for the claws, head or hide or kill grizzlies as a trophy to be shipped out of the country.

"There are a number of issues and unfortunately we don't know the reason on this one," Mr. Mitchell said.

The government estimates there are about 1,100 grizzlies in the province. Biologists and conservationists call the estimate optimistic and figure between 400 and 700 would be more realistic. Either way, in any given population only about half are considered mature, breeding bears.

But while there have been few incidents of poaching in the province, even one has a major impact on the grizzly population.

Jeff Gailus, co-ordinator of the Bow Valley Grizzly Bear Alliance, counts 15 dead grizzlies in and around Banff National Park since June of 2000, most from human interaction.

"In a heavily developed, heavily used area like we have in Southwestern Alberta, it's really difficult to maintain a population of grizzly bears," Mr. Gailus said, ". . . We need a strategy of some kind to stop the unsustainable rate of mortality and to begin to allow the population to recover."