BILLINGS, Mont. (AP) -- The discovery of toxic levels of mercury in bald eagles in Montana has prompted the U.S. Bureau of Land Management to launch a study of the birds in the Yellowstone and Powder River drainages.

Eagles with mercury poisoning turned up last winter at the Montana Raptor Conservation Center in Bozeman. Since then, 10 to 12 more brought to the center showed elevated mercury levels, and two have died.

Officials at the center said the birds came from places throughout Montana, including Red Lodge, Lincoln, Fort Benton and near Dillon.

Gayle Sitter, a wildlife biologist with the BLM in Billings, said the contaminated birds prompted his agency to propose the study.

''We don't have any reason to suspect it's causing any problems, but we want to get some baseline data,'' Sitter said.

The study, scheduled to begin next year, will sample the blood of young bald eagles at about 25 sites. It will look at a number of contaminants, not just mercury, which is both a naturally occurring element and a pollutant associated with coal-fired power plants and other human-related activities.

A similar study is planned for southwestern Montana.

Montana currently has about 400 breeding pairs of bald eagles, compared with just 12 in 1978. A 1972 ban of the pesticide DDT, which caused eagles' eggs to thin and break, and increased protection measures are credited with increasing the population of bald eagles nationwide.