According to local media, Mexican authorities raided 11 iron ore yards at the Port of Lazaro Cardenas—one of the country’s largest seaports—after revelations that drug cartels had been exporting ore to China.

Over 100,000 tons of iron ore was seized, along with 124 bulldozers, backhoes and trucks. The federal security commissioner for western Michoacan state told reporters late Monday that inspectors are testing the ore to determine which mines it came from and whether they were legally registered.

Federal officials said the Michoacan-based Knights Templar drug cartel had been mining, stealing or extorting iron ore for several years.