China says it will open probes into imported U.S. and South Korean solar-grade polysilicon, which is used to make solar products.

The Ministry of Commerce announced Friday that it will investigate whether U.S. and South Korea sold the kind of polysilicon used to produce solar batteries at artificially low prices in China.

In another statement, the ministry said it will look into U.S. state subsidies for the sector, including tax exemptions, free land, and use of public funds for job training.

The announcements come after Washington slapped import duties on solar equipment from China in May, because of what U.S. officials called dumping. Beijing called the action protectionist.