Incursions of red imported fire ant (RIFA), Solenopsis invicta into Korea have been increasing. After a first interception of a colony of S. invicta on Gamman pier, Pusan port while intensive surveillance by Animal & Plant Quarantine Agency (APQA) in September 2017, three more RIFA colonies have been found in sea port piers of Pyeongtek, Incheon and Pusan cities. The social forms and mitochondrial DNA haplotypes of the intercepted RIFA colonies were analysed by allelic discrimination assay (peptide nucleic acid probe based RT-PCR) of Gp-9 gene and mt-DNA fragment of 768 bp, which is part of the Cytochrome oxidaseⅠ gene. The colony on Gamman pier, intercepted in Sep. 2017 was previously reported as a haplotype 5 (H5) of mitochondrial DNA and a social form of polygyne. The colony on Hutchison pier of Pusan port, intercepted in June 2018 were confirmed as a H22 haplotype and a monogyne. Those different social forms show different origins of each colonies. Those on piers of Pyeongtek and Incheon ports, also found in 2018 were confirmed samely as H22 and monogyne. However, it could be putatively assumed that those two colonies were differently introduced via different container cargoes, considering those colonies were found in container yards of distantly located different sea ports. More genetic variation analyses using diverse sets of molecular markers such as microsatellites, genome-wide single nucleotide polymorphisms, etc. in nuclear gens are being proceeded for more exact introduction routes (origins).