The US Commerce Department launched investigations into imports of drones, parts for unmanned aerial vehicles and for polysilicon, a key material for solar power, setting the stage for possible tariffs on those goods.

Drone makers shined on Monday. Red Cat up 20%; Ondas Holdings up 9%; Joby Aviation up 5%.

The probes were launched on July 1 under Section 232 of the Trade Expansion Act, the latest use of that authority by President Donald Trump to review and impose sectoral-specific tariffs into industries deemed critical to national security.

Under the law, the Commerce secretary is expected to deliver the results of an investigation within 270 days. If the probe concludes that importation of the goods under review are a threat to national security, Trump can impose tariffs on those imports.

One investigation is focused on imports of “unmanned aircraft systems (UAS) and their parts and components,” while a separate probe is directed on exports of polysilicon and derivative products to the US.

Trump has already announced investigations under Section 232 for other imports, including copper and pharmaceuticals and has placed levies on steel and aluminum under that authority. Those measures are separate from the country-by-country import taxes the president has also been announcing in recent days as he ramps up his tariff agenda.

The president has unleashed a flurry of tariff demand letters on trading partners, setting rates for import taxes to take effect on Aug. 1. Those moves have riled markets worried that a trade war will pitch the global economy into a downturn and sent trading partners racing to secure deals to avoid the higher rates next month.

Trump on Monday said the US was “barely started” on imposing levies, claiming that his levies have brought in $188 billion in revenue just from car and steel tariffs.