Morris, Minn.-- It has been an unusually harsh winter in far western Minnesota, but spring will come early to a small, cinder block-laboratory at the University of Minnesota. In a few weeks, David Hoope, a herpetolotgist, will awaken three pairs of deformed northern leopard frogs from their hibernation in the lab and attempt to breed them. Hoope wants to find out whether their limb deformities -- missing feet and club feet -- will be passed on to their off-spring in a controlled environment.

Hoppe hopes his experiment will shed light on a biological mystery. Since the discovery of deformed frogs in Minnesota and Wisconsin gained widespread media attention last fall, anecdotal reports of similarly deformed frogs have surfaced in as many as a dozen other states, across southern Canada and even in Japan. The deformities include missing or truncated legs, misshapen legs, extra legs and missing or malformed eyes. Along a 100-mile stretch of the eastern shore of Lake Champlain in Vermont, researchers have confirmed a significant incidence of deformed leopard frogs.

No one knows what may be causing the deformities, or even whether they are, in fact, occurring more commonly than normal. But along with university scientists like Hoppe, researchers from several state and federal agencies are tying to determine how widespread the deformities are and if something unusual in the environment is connected to them.

"There are so many plausible explanations for what's being observed with frogs that we need to first get a lot of data on what's happening," said Gilman Veith, associate director for the Environmental Protection Agency's ecology division.

In addition to studying specimens collected last summer by the EPA's Mid-Continent Ecology lab om Duluth, the agency is setting up a reporting center that will begin analyzing the distribution and extent of the deformed frogs nationwide. This spring, at least three of the agency's 10 regional offices will start field investigations where abnormal frogs have been reported. The agency also plans to begin monitoring amphibian and reptile populations in several national parks, probably including Shenandoah National Park, Veith said.

The National Wildlife Health Center in Madison, Wis., hs already studied about 70 frogs collected in Minnesota last summer. Although nothing has yet been ruled out as a cause of the deformities, preliminary findings suggest that parasites, a leading early theory are not a complete explanation. Kathryn Converse, a wildlife disease specialist at the center, said microscopic tissue analysis determined that some frogs have parasites and some don't regardless of whether they're normal. Researchers at the center have also found no evidence of either viral or bacterial disease, though Converse said a viral infection has not been ruled out.

"This is a real problem. There's a much higher incidence of deformities out there than you'd expect to naturally occur," Converse said. "It's not like we find 300 frogs and one of them has a bad leg."

In December, the National Institute of Environmental Health Sciences, in Research Triangle Park, N.C., sent a five-member team to St. Paul for a briefing at the Minnesota Pollution Control Agency. Officials at the Minnesota agency said they expect to get help from the federal agency, though it is unclear at this point what form that assistance may take. Funding for research on the issue in Minnesota recently became uncertain when the state announced it would defer to federal agencies, prompting accusations that the decision was influence by a fear of the chemical industry -- a charge state officials deny.

Hoppe of the University of Minnesota, whose breeding experiment could help determine whether the abnormalities are genetic, said he expects to apply for research funding from at least one of the agencies interested in the frog problem, but that his work will go forward regardless of government backing.

Hoppe, and his longtime colleague, Robert McKinnell, a cell biologist and cancer expert at the University of Minnesota in St. Paul, were the first scientists to confirm the Minnesota deformities.

McKinnell, who has worked on frogs for nearly 40 years, is studying internal abnormalities in Minnesota frogs he collected last summer -- as well as in specimens he's obtained from the outbreak in Lake Champlain. The Vermont frogs, said McKinnell, are showing deformities identical to those found in Minnesota.

Richard Levey, an aquatic biologist with the Vermont Agency for Natural Resources, said the Lake Champlain deformities were especially striking. Historical records going back almost 80 years reported only five previously know cases of frogs with deformed limbs in the state, he said. Last Oct. 9, Levey and another researcher visited four sites on the eastern shore of Lake Champlain and collected 230 leopard frogs and found 16.5 percent were deformed. Levey said he plans to revisit the same sites this spring and summer.

Jim Mumley, owner of the J.M. Hazen Frog Co. in Alburg, Vt., has been supplying leopard frogs to researchers for 13 years. While he has occasionally seen frogs with missing limbs in the past, this year there were an unusually high number of deformed animals among the 40,000 frogs harvested by the company, he said. "I think there is something to it," Mumley said. "I really do. I just don't know what to make of it. It hasn't had an impact on us yet, but I expect in a year or two it might."