A U.S. expert on North Korea says Pyongyang has likely produced a nuclear warhead.

On Saturday, Japan’s Kyodo News quoted Director of the Asia Program at the Center for International Policy, Selig Harrison, as saying a senior North Korean official suggested that Pyongyang has produced a nuclear warhead that can be loaded onto a ballistic missile.

The report added that the North Korean official had also told Harrison that Pyongyang weaponized all the plutonium it had declared in line with six-nation nuclear agreements.

Harrison disclosed these details and other results of his January trip to Pyongyang during a House Foreign Affairs Committee hearing on Thursday.