President Donald Trump signed an executive order yesterday, directing Secretary of Commerce Wilbur Ross to expedite an existing investigation of aluminum imports.

The investigation was begun under Section 232 of the Trade Extension Act of 1962, which means that a recommendation to restrict imports must be preceded by a finding that the imports in question pose a threat to national security. Last week Trump signed a similar order with regard to a similar Commerce Department investigation probing steel imports.

According to the White House, aluminum imports into the United States increased by 18 percent while US production fell by 47 percent last year. Of the eight aluminum smelters based in the US at the beginning of 2016, seven have either shutdown, reduced production, or are idled.

From 2012 to 2015, imports of semi-fabricated aluminum from China grew by 183 percent. Imports of aluminum foil from China have grown from zero percent of the US market in 2004 to 22 percent today. Employment in the aluminum industry fell by nearly 13 percent from 2015 to 2016.

The Commerce Department’s investigation is to be concluded and a report submitted to the president within 270 days. If aluminum imports are found to impair US national security, the president will have 90 days to determine what action should be taken.