Commercial satellite imagery shows that North Korea is building an unknown type of vessel at a key shipyard that is also being used to equip submarines for missile tests, according to an analysis by 38 North.

The respected Johns Hopkins University website dedicated to analysis of North Korea adds that space images taken on September 21 indicate that previous work suggesting an imminent submarine-launched ballistic missile (SLBM) test have been put on hold.

“Given the continued movement of components in the parts yards, a shipbuilding program is probably underway although the type of vessel remains unknown,” 38 North analyst Joseph S. Bermudez Jr. wrote of the activity at North Korea’s Sinpo South Shipyard.

At the same time, Bermudez said: “There are no activities suggesting either previous or forthcoming ejection tests at the facility’s test stand.” Bermudez has been analyzing imagery of the site and reported earlier that an SLBM test from a special barge located at the shipyard might occur soon.

Bermudez cautioned, however, that a SINPO-class submarine, submersible test stand barge and nearby test stand at the site “appear capable of supporting a test at any time of Pyongyang’s choosing.”

North Korea is focusing on developing submarines that can launch nuclear-tipped missiles at the US and its allies.