The U.S. State Department believes North Korea is likely to possess additional nuclear facilities beyond those already known at the Yongbyon complex, a report published on June 5 says.

The 2015 Report on Adherence to and Compliance With Arms Control, Nonproliferation, and Disarmament Agreements and Commitments contains the comments and was presented to the U.S. Congress last week.

“The United States believes there is a clear likelihood of additional unidentified nuclear facilities in the DPRK,” the report reads in its assessment of North Korea’s adherence to the Nuclear Non-Proliferation Treaty (NPT).

North Korea acceded to the NPT in 1985 but