Chinese customs authorities have reportedly seized 70 kilograms of the rare metal “vanadium” that was bound for North Korea.

Japanese broadcaster NHK said Wednesday that authorities at Dandong city in northeastern Liaoning Province found the stash of the rare metal hidden in six fruit boxes on a truck bound for the North last Friday.

The Chinese government strictly bans exports of vanadium, which is used to produce airplane and missile parts.

NHK said China was trying to demonstrate its determination to efficiently implement U.N. sanctions against Pyongyang with the recent seizure.