SEOUL, South Korea — South Korea said Saturday that tests on dead pigs from two farms near its border with North Korea came back negative for African swine fever, at least temporarily easing fears over the spread of the illness that has ravaged pig herds across Asia.

South Korea's Ministry of Agriculture, Food and Rural Affairs said it will continue to maintain an elevated level of quarantine and preventive efforts at farms near the border following an outbreak that was confirmed earlier this week.

Workers have so far culled more than 10,000 pigs to contain the disease after the country's first two cases were confirmed in the towns of Paju and Yeoncheon, which are near the border. The North reported an outbreak near its border with China in May.

Officials had tested samples of three dead pigs from two other farms in Paju on Friday after they were suspected of African swine fever infection.

African swine fever is harmless to people but fatal and highly contagious for pigs, with no known cure. In South Korea, where diets rely heavily on pork, there is concern that the outbreak could spread and hurt an industry with 6,300 farms raising more than 11 million pigs. The disease decimated pig herds in China and other Asian countries before reaching the Koreas.

The agriculture ministry said the next three weeks will be crucial for fighting the outbreak, considering the disease's incubation periods.

Officials stepped up efforts to disinfect farms and vehicles and banned border area farms from transporting their pigs to other areas. They also plan to install more traps, nets and fences to capture or repel wild boars that roam in and out of North Korea, which some experts see as a potential source of the outbreak in South Korea.

North Korea in recent months has virtually scrapped all diplomatic activity and cooperation with South Korea amid a standstill in nuclear negotiations with the United States, complicating efforts at preventing the North Korean outbreak from spreading to areas near the border.