Ukraine is being shaken by one of the biggest wartime corruption scandals since Russia’s invasion three years ago, after investigators raided the homes of top officials and a former business partner of President Volodymyr Zelenskyy as part of an investigation into an alleged sprawling corruption scheme in the country’s energy sector.

Ukraine’s main anti-corruption agencies on Monday announced they had uncovered the “high-level” scheme that included corruption at Ukraine’s state nuclear energy company Energoatom. The National Anti-Corruption Bureau said it has proof that the scheme had elicited kickbacks worth $100 million from contractors hired to build defenses for Ukraine’s energy infrastructure to protect it from Russian attacks. That is likely to draw particular outrage from Ukrainians as it affects the efforts to guard the country’s power systems, as they come under sustained attack from Russia.

On Tuesday, NABU said it had detained five individuals and notified seven “members of the organisation of their status as suspects,” saying they included “a businessman who is the head of the criminal organisation” and “a former advisor to the Minister of Energy,” as well as a former deputy prime minister.

The agencies hadn’t initially named the individuals, but Ukrainian media reported one is the former business partner and close associate of Zelenskyy, Tymur Mindich.

A wealthy businessman, Mindich co-owned Zelenskyy’s production company, Kvartal 95, from the president’s years as an actor until Zelenskyy transferred ownership when he was elected. He has previously faced allegations of exploiting his connections with the president, according to Ukrainian media.

On Tuesday, prosecutors from the Specialized Anti-Corruption Prosecutors’ Office reportedly named Mindich, along with six others, during an arraignment hearing for one of the suspects in the energy scheme, according to local media.

NABU said it had raided Mindich’s house on Monday but that he had fled the country, prompting speculation he could have been tipped off.

Ukrainian media also report that the FBI is now also investigating Mindich. ABC News has reached out to the FBI for a comment.

Ukraine’s Justice Ministry on Tuesday also confirmed that its minister, German Galushenko, was also part of the investigation after it was reported that NABU agents had raided his home.

There are so far no allegations that Zelenskyy himself was involved in the corruption scheme, but the allegations against a former close associate are potentially embarrassing and have prompted warnings from anti-corruption activists that the president must ensure the investigation is allowed to proceed.

Zelenskyy this summer also moved to take more control over the same anti-corruption agencies now investigating the energy sector corruption scheme. That attempt triggered the first mass protests of the war and criticism from European allies, forcing Zelenskyy to back down.

The new allegations come at a moment when Ukraine is struggling to protect its energy infrastructure from the heaviest Russian attacks of the war, which have left most of the country frequently living with rolling blackouts. Zelenskyy has been seeking financial support from Western countries to help restore the system and provide greater defenses.

The scandal could also risk reigniting problems for Zelenskyy with President Donald Trump, given some influential right-wing allies have long accused the Ukrainian leader of corruption. The alleged involvement of senior government ministers could also hurt morale among Ukraine’s public amid the war.

Zelenskyy on Monday expressed support for the investigations and said convictions must follow.

“Everyone who has built corrupt schemes must face a clear procedural response,” Zelenskyy said in his nightly video address. “There must be convictions. And government officials must work together with NABU and law enforcement bodies — and do it in a way that delivers real results.

Prominent Ukrainian anti-corruption activists have now said the president must prove that he will hold his associates accountable.

Daria Kaleniuk, a veteran campaigner, wrote that if there are fresh moves against the anti-corruption agencies, NABU and SAPO, “it will be a clear sign that the president decided to cover up his friends instead of supporting justice and interests of the nation of Ukraine.”