China's Ministry of Commerce (MOFCOM) on September 20 began imposing provisional anti-subsidy duties on some U.S. exports of solar-grade polysilicon, a major material for making solar cells.

MOFCOM said a preliminary investigation found that some solar-grade polysilicon imports from the United States were subsidized, which had caused substantial damage to Chinese producers.

Chinese importers of the product from U.S. companies, including Hemlock Semiconductor Corp. and AE Polysilicon Corp., are required to pay a deposit rate of up to 6.5 percent.

Other companies, including REC Solar Grade Silicon LLC, REC Advanced Silicon Materials LLC and MEMC Pasadena, Inc., would not be subject to such duties because they had not been subsidized or the rates were too low.

The decision comes after MOFCOM slapped anti-dumping duties of 53.3 percent to 57 percent on U.S. solar-grade polysilicon imports in July.