BERLIN (AP) — Authorities were searching the European Parliament office of a prominent German far-right lawmaker in Brussels on Tuesday, Germany’s top prosecutor’s office said.

Maximilian Krah, the Alternative for Germany party’s top candidate in the upcoming European Parliament elections, has been under scrutiny after an assistant of his was arrested last month on suspicion of spying for China.

Jian Guo — a German national who had worked for Krah since his election to the European Union legislature in 2019 — has been accused of of working for a Chinese intelligence service and of repeatedly passing on information on negotiations and decisions in the European Parliament in January. Prosecutors allege that he was also spying on Chinese dissidents in Germany.

The arrest cast an unflattering light on the far-right Alternative for Germany, or AfD, which already faced criticism for having Russia-friendly positions. The European Parliament elections will take place June 9 in Germany.