One key question in North Korea’s efforts to develop missiles that can hit the US and its allies is whether Pyongyang is capable of producing a critical liquid rocket engine fuel called UDMH.

UMDH (short for unsymmetrical di-methyl-hydrazine) is a stable propellant that can be kept loaded in rocket fuel systems for extended periods. Some analysts believe the North is already using UMDH for its Hwasong-12 mobile intermediate-range ballistic missile and Hwasong-14 mobile intercontinental ballistic missile systems.

Analyst Jeffrey Lewis has previously speculated that UMDH is being produced at the February 8 Vinalon Complex in Hungnam based on satellite imagery of the site.

But 38 North said in a Wednesday article that additional locations in North Korea may be involved in UMDH production. The respected Johns Hopkins University website dedicated to analysis of North Korea says one likely site is the July 27 Factory also known as, Aoji-ri Chemical Complex. Another strong candidate for UMDH-related activities is the Hungnam Fertilizer Complex.

While it’s never been confirmed that North Korea has the actual capability to produce UMDH, the 38 North article says Pyongyang is aware of the critical need for domestic production and in all probability is addressing the problem.

“While most analysts agree that North Korea possesses the scientific and industrial capability to produce UDMH, no firm open source evidence has been found confirming this notion. However, the failure to domestically produce the fuel would represent an extremely vulnerable single-point-of-failure that the North understands well and has most likely addressed, given known historical practices within its arms production industry,” 38 North analysts Joseph S. Bermudez Jr., Michael Elleman and Curtis Melvin wrote in the exclusive analysis.

The article says the North’s first access to UDMH technology likely occurred around 1992 when it acquired technology and engineers from the Russian Isayev and Makayev Design Bureaus.