At least a dozen North Korean ships were active in September despite ongoing port lockdowns to prevent the spread of COVID-19, according to recent Automatic Identification System (AIS) data.

Ships use AIS data to avoid colliding with each other — a system that’s critical to have while traversing narrow, high-traffic areas like the Korea Strait. North Korean ships are good at masking their identities on AIS, but some can still be tracked.

In September, several ships traveled to secondary Chinese trade routes. Some made trips to a key coal-smuggling hotspot at China’s Zhoushan Islands, near