All five-thousand-nine-hundred red fire ants that were discovered inside a container in Ansan were found dead on Tuesday.
According to the South Korean Environment Ministry, the red fire ants were all killed after the container was fumigated on Monday.
No queen ant was found, but there was one princess ant, an unfertilized female in the process of becoming a queen, inside the container.
This is the eighth time that red fire ants have been reported in South Korea, with the first report coming last September.
Red fire ants are classified as one of the world's top 100 malign invasive species by the International Union for Conservation of Nature.