Two major South Korean retailers have temporarily stopped selling U.S. beef after mad cow disease was discovered in a dairy cow in California.

South Korea's No. 2 and No. 3 supermarket chains, Home Plus and Lotte Mart, have "temporarily" halted sales of U.S. beef to calm worries among South Koreans.

"We stopped sales from today," said Chung Won-hun a Lotte Mart spokesman. "Not that there were any quality issues in the meat but because consumers were worried."

The U.S. Department of Agriculture (USDA) confirmed the country’s fourth case of mad cow disease in a dairy cow in California on Tuesday, but urged that there was no public health risk.

According to a statement released by USDA Chief Veterinary Officer John Clifford, the cow had not entered the food supply. Clifford said the animal’s carcass is being held at a rendering facility and will be destroyed.

It has not been revealed where the cow originated, but a senior manager with a California rendering company says they discovered the cow had the disease while it was at his Hanford, California, transfer station.

Dennis Luckey, executive vice president of Baker Commodities in Los Angeles, told The Associated Press the disease was discovered after workers selected the cow for random sampling.

The sample was taken from the dead cow's carcass on April 18 at a hide-removal site, he said.

"This animal happened to be one that we randomly selected," Luckey said.

The company does not yet know which farm the cow came from, but the animal never made it to Baker's rendering plant 50 miles away in Kerman, California, Luckey said.

Samples of the cow tested positive for atypical bovine spongiform encephalopathy (mad cow disease), a very rare form of the disease that is usually not associated with animals consuming infected feed.

The Agriculture Department is sharing its lab results with international animal health officials in Canada and England, Clifford said.

The news spread quickly in South Korea, which imposed a ban on U.S. beef in 2003 along with China and other countries because of mad cow disease concerns. Seoul's resumption of U.S. beef imports in 2008 sparked daily candlelight vigils and street protests for several months as many South Koreans still regarded the meat as a public health risk.

South Korea imports U.S. beef from cows less than 30 months old and there is no direct link between U.S. beef imported into South Korea and the infected animal, the country's agriculture ministry said in a statement.

That did not kept South Korea from taking further measures. The ministry decided to beef up inspections on U.S. beef and request detailed information on the infected cow from the United States, an initial measure to appease public concern while avoiding possible trade conflicts.

"We are still reviewing whether we will stop quarantine inspections," Chang Jae-hong, deputy director of the ministry's quarantine policy division, told the Associated Press by phone. Halting quarantine inspections can suspend the delivery of U.S. beef sales at local retail channels.

"Information we have is too limited so we asked for more details from the United States," Chang said.

At a Home Plus store of southwestern Seoul, people were scant at the meat section on Wednesday afternoon. Some consumers said they were not worried about the mad cow as long as officials said they pose no health risks.

But others criticized that the U.S. government was "arrogant" and "inconsiderate" to say the discovery of tainted cow would have no impact on its meat exports.

"I won't eat meat from the countries where mad cow disease was found," said Kim Woo-sig, a 47-year-old self-employeed.

No other Asian countries immediately announced they are halting sales of U.S. beef.

BSE is a fatal neurological disease among cattle, “causing them to display nervousness or aggression, abnormal posture, difficulty in coordination and rising, decreased milk production, or loss of body weight,” the USDA’s statement said.

According to the Centers for Disease Control and Prevention (CDC), there is strong evidence of a causal relationship between BSE and varient Creutzfeldt-Jakob Disease (vCJD) in humans. VCJD is a rare, and typically fatal, degenerative brain disorder that is characterized by prominent psychiatric symptoms and neurological abnormalities such as ataxia and dementia.

There have only been a few cases of vCJD confirmed in people living in the U.S., but those were linked to meat products in the United Kingdom and Saudi Arabia, according to the CDC.

Click here to read more from the USDA.

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The Associated Press contributed to this article.