While the United States warns the international community about Chinese espionage, German officials raided nine properties in an effort to crack a Chinese spy ring involving a former European Union diplomat, according to reports.

“I can confirm that we are carrying out an investigation into intelligence agent activity,” Markus Schmitt, a spokesman for German federal prosecutors, said Thursday.

The statement marks a rare revelation of the shadowy struggle between rival intelligence agencies. The investigation stretches from Brussels, where the headquarters of the European Union is, to Berlin and other German districts, lending weight to U.S. efforts to convince the European allies to be more suspicious of Chinese espionage threats.

“At the center of the investigation is a former employee of the EU Commission and later diplomat of the European External Action Service,” according to Der Spiegel, which first reported on the probe. “In his role for the EU, he held leadership positions in Brussels; later he was EU ambassador to several countries.”

The suspected spy has not been named, and German officials have not made any arrests in the case. Chinese officials brushed off questions about the raid.

“I'm not aware of this,” Chinese Foreign Ministry spokesman Geng Shuang told reporters on Thursday.