South Korea says the strategic metal “vanadium” recently seized by Chinese authorities from a North Korea-bound truck is not on international export ban lists.

Officials from the Foreign Ministry and the Korea Strategic Trade Institute said vanadium is not a contraband item restricted by the Missile Technology Control Regime (MTCR) and the Nuclear Suppliers Group (NSG).

The officials say the export of the metal is not banned under United Nations Security Council Resolutions 1718 and 1874, either.

A ministry official said that China may have wanted to demonstrate its determination to faithfully implement U.N. sanctions against the North by announcing its confiscation of the metal.

Chinese authorities seized 70 kilograms of vanadium on Friday in Dandong on the Chinese border with the North. The rare metal is used to produce airplane and missile parts.