The US Commerce Department said it will investigate U.S. producer complaints that wind-tower manufacturers from China and Vietnam sell their renewable-energy equipment below cost in the US.

The Wind Tower Trade Coalition, which includes Broadwind Energy Inc., Otter Tail Corp.’s DMI Industries, a unit of Trinity Industries Inc. and Katana Summit, said competitors from both nations use unfair pricing to win sales in the US, according to a petition filed with the agency on Dec. 30.

The Commerce Department and International Trade Commission separately have decided to investigate an Oct. 19 complaint from US solar manufacturers who say they are being harmed because China’s government uses cash grants, discounts on raw materials, preferential loans and tax incentives to benefit Chinese companies.

The investigations may add tensions between the world’s two largest economies, which have clashed over access to each others’ markets for products including steel pipes, poultry, tires, movie and music.

“The evidence of material injury and threat of additional material injury by Chinese and Vietnamese imports are overwhelming,” Alan Price, a lawyer at Wiley Rein LLP for the companies, said on January 20 at a meeting with staff from the US International Trade Commission, which is conducting a separate investigation. “What should be a growing, profitable and developing portion of the renewable-energy industry is instead fighting for its survival today.”