BEIJING (Reuters) - China found its second case of African swine fever (ASF) on Thursday at a slaughterhouse owned by WH Group Ltd’s Chinese unit, stirring concerns about the spread of the deadly infection across the world’s largest pig herd.

Some 30 hogs died of the disease at the slaughterhouse in Zhengzhou in central Henan province, the Ministry of Agriculture and Rural Affairs said in a statement. The pigs had traveled thousands of kilometers from a farm in Jiamusi city in China’s northeastern province of Heilongjiang, it said.

Local authorities suspended operations and sealed off the slaughterhouse, controlled by China’s largest pork processor Henan Shuanghui Investment & Development, a subsidiary of WH Group, a WH spokeswoman confirmed with Reuters.

The outbreak comes almost two weeks after another northeastern province, Liaoning, culled thousands of pigs after the discovery of China’s first case of African swine fever.

The agriculture ministry did not name the company in Zhengzhou, but Shuanghui Investment & Development reported earlier on Thursday that it had discovered a suspected case of the disease, a director of the Heilongjiang Provincial Animal Husbandry and Veterinary Bureau told Reuters.

Heilongjiang authorities were investigating whether the pigs were infected in the northeastern province bordering Russia. The provincial veterinary official said it wasn’t clear where or how the pigs in Zhengzhou caught the disease.

“We have sent two batches of experts from the (Heilongjiang) province and central government to Tangyuan this morning, where the suspected outbreak was reported,” the official said.

Tangyuan is a county in Jiamusi city.

Shuanghui has diverted orders from its Zhengzhou operations and is cooperating with the authorities to contain the disease, a staff member in the media relations department of Shuanghui said.

Neighboring factories will supplement supplies and sales from the slaughterhouse during its suspension. Shuanghui’s production capacity and production in the region will not be affected, the WH spokeswoman said.

The pigs in question did not enter the slaughtering process because the problem, later identified as ASF, was discovered before that, the spokeswoman said.

After the first outbreak in Liaoning, which was also the first in East Asia, Japan suspended imports of heat-treated Chinese pork and has tightened quarantine operations at airports and seaports.

VAST DISTANCE

The vast distance the pigs in Henan traveled - some 2,300 km (1,440 miles) southwest from Heilongjiang to central China - highlights the challenge for the government in controlling the highly contagious disease in the country’s vast hog population and beyond its borders.

Henan is China’s second-largest pig producer, and is a big supplier to nearby Shandong, Sichuan and Hubei provinces.

“The issue is quite serious now that the disease just hit the center of pig production,” said Yao Guiling, an analyst at consultancy China-America Commodity Data Analytics.

“The outbreak might be more severe than just the two cases that have been confirmed.”

Shares in Shuanghui sank 10 percent on Thursday amid concerns about the impact of the disease on sales. Other large hog farmers, Muyuan Foods Co and Guangdong Wens Foodstuff Group Co, were also sharply lower.

The disease is the latest blow to Chinese hog farmers, who have been struggling with a prolonged rout as years of frenzied investment to boost production have created oversupply, with output well beyond stagnating domestic demand.

ASF is one of the most devastating diseases to affect swine herds. It occurs among pigs and wild boars, transmitted by ticks and direct contact between animals, and its effects are often deadly. There is no vaccine.

The disease does not affect humans.

Shuanghui, headquartered in Luohe, Henan province, has 15 slaughterhouses, with a total annual capacity of 30 million hogs, and 23 production bases across China, spanning from Heilongjiang to the southern province of Guangdong.

Shuanghui sells more than 3 million tonnes of pork a year.

(This version of the story was refiled to remove WH Group was not available for comment in paragraph 21)