A secretive North Korean agency in charge of missile and nuclear weapons development sent over 1,000 workers to China and sold electronics to Iran with the assistance of DPRK nationals in Beijing, according to the U.S. Treasury on Thursday.

The Office of Foreign Assets Control (OFAC) lays out the claims in a new sanctions notice, implicating China in the weapons material procurement but only designating two North Koreans, one of whom reportedly works for the DPRK Embassy in Beijing.