Ukrainian authorities have arrested former energy minister German Galushchenko as he tried to leave the country. Galushchenko, who resigned last year amid a major corruption scandal, is now facing questioning in Kyiv.

He is accused of taking kickbacks from contracts at Ukraine’s national nuclear operator Energoatom, with investigators saying contractors paid between 10% and 15% of contract values in illegal fees. Some of the money was reportedly laundered and sent abroad, including to Russia.

The arrest is part of Operation Midas, a 15-month anti-corruption investigation led by Ukraine’s National Anti-Corruption Bureau (NABU) and the Specialized Anti-Corruption Prosecutor’s Office (SAP).

The probe has implicated several high-profile officials, including former Deputy Prime Minister Oleksiy Chernyshov and Svitlana Hrynchuk, Galushchenko’s successor as energy minister, both of whom resigned or were arrested. Businessman Timur Mindich, co-owner of President Volodymyr Zelensky’s former TV studio, reportedly fled the country after being flagged as a suspect.

The scandal, valued at around $100 million, caused public outrage, especially as it came during a period of intensified Russian attacks on Ukraine’s energy infrastructure in the winter.

While Zelensky and his top aide Andriy Yermak have not been accused of wrongdoing, the case has increased pressure from international partners, including the U.S., to hold elections that have been postponed since the start of the war in 2022.

Galushchenko has stated he plans to defend himself against the allegations. Ukrainian authorities say cracking down on corruption is crucial for the country’s efforts to join the European Union.