The future of Southeast Asia’s booming solar industry, which produces the most panels in the world after China, is being thrown into doubt as the United States looks set to impose hefty tariffs on the region.

Chinese firms that set up factories there over the last decade are now being accused of skirting U.S. import levies on their home market.

At least three — including Longi Green Energy Technology Co. and Trina Solar Co. — have scaled back operations in Thailand, Vietnam and Malaysia, which, along with Cambodia, are being targeted by Washington.