The trade dispute that has embroiled EU and China relations is heating up with the onset of an “anti-dumping probe” into Chinese solar panels.

Financial Times reports that the EU announced the investigation on Thursday following complaints from German company Solarworld, which accused Chinese manufacturers of selling solar panels  underpriced by 60 to 90%. Solarworld previously took the complaint to the US, prompting Washington to impose anti-dumping tariffs and countervailing duties on Chinese solar panel manufacturers earlier this year. The EU solar market is the world’s largest and accounted for 21 billion Euros of China’s solar exports last year.

Beijing said that the probe could have “negative impacts” on the countries’ commercial ties and threatened to take retaliatory trade measures. “Restricting China’s solar panel products will not only be damaging to industries in both China and the EU, but will also destroy the health development of the solar and renewable energy sectors around the world,” China’s ministry of commerce said in a statement. Chinese solar panel manufacturer Yingli claimed that the EU’s trade complaint was “groundless”.

“What we really hope is that the European Commission will take action earlier because we are losing companies in Europe week by week,” Eu ProSun group director Milan Nitzschke told the FT.