China is opening an investigation of whether the U.S. has unfairly subsidized raw materials for solar panels destined for Chinese manufacturers, or whether U.S. companies have been selling these materials at unfair prices.

The move seems to be in retaliation to large tariffs recently imposed by the United States on solar panels imported from China, alleging unfair trade practices. Those tariffs seem to be having an effect on imports from China, which have fallen by 45 percent, according to the Coalition for American Solar Manufacturing.

For more on the tariffs, see “Could Tariffs on Chinese Solar Panels Do More Harm than Good?” and “How Will Tariffs on Solar Panels Affect Innovation?”

At least two defunct U.S. solar companies, Abound and Solyndra, have blamed their failure on unfair Chinese trade practices. For a look at what it might take for similar companies to succeed, see “Can Energy Startups Be Saved?”