The US Commerce Department on Thursday opened an investigation into whether China and Taiwan are dumping a certain class of solar cells into the US market at below fair market value.

Launching the latest round in an ongoing dispute with China over solar energy products, the department took aim at some $2.6 billion in imports of certain crystalline silicon photovoltaic products from the two countries.

The imports include crystalline silicon photovoltaic cells, modules, and panels, by themselves or integrated into other products.

The probe will also extend to whether China is also unfairly subsidizing the same class of products, or a countervailing duty investigation.

The probe was requested by a large US solar panel manufacturer, SolarWorld Industries America of Hillsboro, Oregon..

In 2012, the United States imported crystalline silicon photovoltaic products from China and Taiwan valued at an estimated $2.1 billion and $513.5 million, respectively.

The scope of the new investigation excludes crystalline silicon photovoltaic cells from China that already are under anti-dumping orders.

Solar products have been a focus of friction between China and the United States, which accuses the Chinese government of unfairly subsidizing the industry to gain a trade advantage.

The US International Trade Commission will make its preliminary decision on whether the US company has been injured by underpriced and subsidized Chinese and Taiwanese products by February 14.

After that, the Commerce Department will decide whether to levy anti-dumping and anti-subsidy duties on the products between March and June.