Construction has resumed and expanded on a project to upgrade a key North Korean nuclear missile factory, according to NK Pro analysis of satellite imagery, as the munitions industry enters the final stretch of leader Kim Jong Un’s five-year weapons development plan.

The expansion project at the Thaesong Machine Factory near Pyongyang, believed to be involved in long-range missile engine production, started last July before progress halted between early December and mid-March.

Planet Labs satellite imagery now shows that work resumed in the second week of March on new buildings outside entrances to underground