South Korea has confirmed a second case of African swine fever near its border with North Korea, raising concerns that the outbreak could spread and wreak havoc on the country's massive pig herds.

An official from South Korea's agriculture ministry said Wednesday that workers were planning to cull some 5,000 pigs raised at a farm in the town of Yeoncheon after the highly contagious disease was confirmed in tests of a dead pig.

Officials culled nearly 4,000 pigs and stepped up quarantine efforts Tuesday after confirming the country's first case of the disease.

Quarantine officials wearing protective gear stand as a precaution against African swine fever at a pig farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. The notice reads: "Under quarantine." (AP PhotoAhn Young-joon)

Quarantine officials wearing protective gear stand as a precaution against African swine fever at a pig farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. The notice reads: "Under quarantine." (AP PhotoAhn Young-joon)

African swine fever has decimated pig herds in China and other Asian countries before reaching the Koreas. It is harmless to people but for pigs is highly contagious and fatal. There is no known cure.

A quarantine official wearing protective gear patrols as a precaution against African swine fever near a pig farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. (AP PhotoAhn Young-joon)

A quarantine official wearing protective gear patrols as a precaution against African swine fever near a pig farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. (AP PhotoAhn Young-joon)

Backhoes prepare to dig a pit to bury culled pigs at a farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. (AP PhotoAhn Young-joon)

Backhoes prepare to dig a pit to bury culled pigs at a farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. (AP PhotoAhn Young-joon)