According to data released Sunday by China’s General Administration of Customs, exports of rare earth magnets to the U.S. reached 353 metric tons in June, a more than sevenfold increase compared with May and a rise of 660%.

China's exports of rare earth magnets to the United States in June soared to more than seven times their May level, marking a sharp recovery in the flow of critical minerals used in electric vehicles and wind turbines after a Sino-U.

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