SEOUL (Reuters) – South Korea on Wednesday confirmed a sixth case of African swine fever in a town near its border with North Korea, while another suspected case tested negative, the Agriculture Ministry said.

Six cases have been reported since mid-September in South Korea, prompting the country to raise its animal disease alert level to the highest and step up disinfection measures.

Test results of another suspected case of the virus reported in Yeoncheon, northwest of the capital Seoul, came back negative, the ministry said.

More than 20,000 pigs had been slaughtered as of Tuesday, with another some 30,000 expected to be culled as a preventative measure.

That would be 0.4% of the country’s pig population of some 12.3 million pigs.

(Reporting by Joori Roh, Jane Chung; Editing by Jason Neely and Alison Williams)