The CEO of Russia’s leading power engineering company was detained by the Federal Security Service (FSB) on Thursday over a case involving the alleged disclosure of state secrets, the Interfax news agency reported.

Roman Filippov, head of St. Petersburg-based AO Power Machines, Russia’s largest maker of turbines for power stations, had his office and home searched by the FSB, the Fontanka news website reported.

Power Machines has several joint ventures in Russia with Germany’s leading power engineering company, Siemens.

Filippov’s questioning comes days after Siemens filed a lawsuit against Russian state firm Technopromexport for allegedly sending the German company’s turbines to Crimea when they were slated for a separate project in southern Russia.

“We received information from reliable sources that at least two of the four gas turbine units that were delivered for the project in Taman in the south of Russia were transferred to Crimea against our will,” Kommersant newspaper reported the company as saying.

After Russia’s annexation of the Crimean pinnusula in 2014, it has been subject to European sanctions on energy and technology. The row has raised concerns over Seimens’ compliance of those sanctions.

Germany’s ambassador to Russia, Rudiger von Fritsch, said if Siemens had been deceived it would “seriously undermine trust and would be a major setback for investment in Russia,” the Interfax news agency reported.