China’s Ministry of State Security says it is cracking down on alleged smuggling of rare earths materials that it says threaten national security.

China’s exports of rare-earth products jumped in June, pointing to a potential pickup in magnet supplies after government-imposed curbs that proved to be Beijing’s most powerful weapon in its trade war with the Trump administration.

China arrests suspects involved in smuggling strategic minerals, and authorities warn of ‘increasingly covert’ tactics to evade detection.