Authorities quarantined a calf from the cow, along with about 400 other animals, at a Sunnyside bull calf feeding operation. The U.S. Department of Agriculture did not release the name of the business, and the state Department of Agriculture did not immediately respond to a request for registration documents for feed operations in Sunnyside, about 8 miles north of Mabton.

Another calf remained under quarantine with the rest of the dairy herd in Mabton, where the animal that tested positive for the brain-wasting disease came from.

"The reason for concern with these calves is that even though it is an unlikely means of spreading the disease, there is the potential that the infected cow could pass the disease onto its calves," said Dr. Ronald DeHaven, the USDA's chief veterinarian.

A government source familiar with the investigation told The Associated Press the infected cow came from the Sunny Dene Ranch in Mabton, about 40 miles southeast of Yakima. Without releasing the farm's name, USDA officials have said a dairy in Mabton is under quarantine and that its herd would be slaughtered if the mad cow diagnosis was confirmed.

"We have not made any decisions on the disposition of the herd," DeHaven said.

Mike Louisell, spokesman for the state Department of Agriculture, said a slaughter "is being discussed, but no decisions have been made."

An unidentified man who answered the phone at the Sunny Dene Ranch Friday said the USDA has asked the family not to comment.

Charles Powell, spokesman for Washington State University's College of Veterinary Medicine, said he spoke with one of the dairy's owners, veterinarian Dr. William Wavrin.

"I do know that his operation is held in very high esteem in this college by our large animal practitioners and also the field disease investigation unit," Powell told the AP. "A bad thing has happened to a very good person who does very good work."

Business appeared to continue as usual at the dairy Friday.

Dan Senn, an independent contractor from Granger hired to artificially inseminate cows at the dairy, said he was going ahead with his work until told otherwise.

State Agriculture Department officials were helping federal investigators trace both the animal's history and what happened to the meat from its carcass. "That's what we're doing, whatever's needed," Deputy Agriculture Director Bill Brookreson said.

The emphasis of the widening investigation is on finding the birth herd of the slaughtered cow, since it likely was infected from eating contaminated feed. The incubation period for mad cow disease, or bovine spongiform encephalopathy, is four to five years.

"It could be from Washington state, it could be from another state, it could be from Canada," Louisell said. "At this point there's not even speculation."

"This case is going to get resolved, in our opinion," he said. "We just don't have all the answers yet."

Federal authorities said they were looking at two possible businesses that may have sold the infected cow to the Mabton farm in October 2001.

One is a livestock market and the other is described as a finishing facility for dairy heifers. Officials did not name either business.

"We are only day three in what will no doubt be a very complex and complicated investigation," DeHaven said.

The case has brought international attention to Mabton, a town of 2,045 people. Dozens of dairies dot the area's hills, along with fields of hops and wine grapes.

Residents have grown weary of the spotlight and worry about their future.

"I know this is a concern and I don't want to make light of it, but I would hope that as time goes on we can move forward and get past this," Mayor David Conradt said.

Anything that affects farmers, affects farm workers and the businesses that serve all those people, he said. "Depending on how far-reaching this is, the impact could be tremendous."

Meanwhile, government and cattle industry officials continued to voice assurances that the beef on American tables was safe to eat.

The USDA said the cow was slaughtered at Vern's Moses Lake Meat Co. in Moses Lake, about 70 miles northeast of Mabton, on Dec. 9, after she became paralyzed, apparently as a result of calving.

Agriculture officials said Vern's was voluntarily recalling about 10,410 pounds of raw beef, but the agency's Food Safety and Inspection Service said there was an "extremely low likelihood" that the recalled beef contains the infectious agent for BSE.

BSE eats holes in the brains of cattle. A human disease related to mad cow is known as variant Creutzfeldt-Jakob disease. It is incurable and was blamed for 143 deaths in Britain, which suffered a mad cow disease outbreak in the 1980s.

The USDA said the slaughtered cow was deboned at Midway Meats in Centralia, and the meat - though no contaminated spinal or brain tissue - was sent to two Oregon processing plants, Willamette Valley Meat Co. and Interstate Meat Distributors Inc. in the Portland metropolitan area.

There are 1.1 million cattle in Washington state, including 247,000 dairy cows, according to the Washington State Beef Commission. About 9,500 farmers and ranchers make their living from the cattle industry, with gross income of $621 million last year.

For More Information:

USDA -- www.usda.gov
CDC Fact Sheet -- www.cdc.gov
CDC General Info -- www.cdc.gov