The Unification Ministry has begun, in collaboration with relevant authorities, cracking down on possible imports of North Korean products through a third country.

A ministry official said customs offices nationwide will be subject to on-site investigations that will begin in Incheon on Thursday and will open before Monday in Busan, Pyeongtaek and Gunsan.

The official said, however, that actual cases where North Korean products have been illegally brought into South Korea via a third party have not been detected.

The South Korean government announced on May 24th that the nation would halt all trade with North Korea except with the inter-Korean run Gaeseong Industrial Park. It has since stepped up customs inspections on products that are likely to be illegally brought in from North Korea, such as anthracite, clams, and bracken.

The sanctions are retaliatory measures for the North’s March sinking of South Korea’s “Cheonan” naval vessel.