In the notice posted on the Federal Register, the department's Bureau of Industry and Security said that Commerce Secretary Howard Lutnick initiated the investigation on May 1 under Section 232 of the Trade Expansion Act of 1962, reports Yonhap news agency. Under Section 232, the president is provided with authority to adjust imports into the U.S. when he determines they threaten national security. Trump has been using tariffs to generate federal government revenue, reduce America's trade deficit, draw in foreign investments and strengthen domestic manufacturing. The department plans to collect public comments for 21 days from the official publication of the notice. Using Section 232, Trump has already imposed 25 percent tariffs on automobiles and steel. His administration has also been conducting probes to determine national security effects of imports of copper, lumber, semiconductors and pharmaceuticals, among other items. Meanwhile, a coalition of 15 US states is filing a new lawsuit challenging President Donald Trump's executive order declaring a "national energy emergency," which aims to accelerate fossil fuel development. Washington State Attorney General Nick Brown announced the legal action on Friday during a press briefing. The 61-page complaint was submitted to the US District Court for the Western District of Washington. According to the lawsuit, Trump's order violates the National Emergencies Act of 1976, which was designed to ensure that presidents use their emergency powers "only when actual emergencies exist" and not for "frivolous or partisan matters. "Prodded onto the shakiest of limbs by the President's unsupported and unlawful Executive Order, multiple federal agencies now seek to broadly employ these emergency procedures in non-emergency situations," the lawsuit said.