Delegation members attending peace talks between Ukraine and Russia suffered symptoms of suspected poisoning after a meeting in Kyiv earlier this month, according to a report in The Wall Street Journal.
Russian billionaire Roman Abramovich and at least two senior members of the Ukrainian team, including Crimean Tatar lawmaker Rustem Umerov, were affected, according to the newspaper, which cited people familiar with the matter.
It said the delegation members showed symptoms that included red eyes, constant and painful tearing, and peeling skin on their faces and hands. The health of those affected has since improved, and their lives are not in danger, according to the report.
Investigators for the open-source collective Bellingcat were also involved in sourcing the WSJ report.
Bellingcat said its sources had confirmed the events, citing experts who had investigated the matter and concluded that "poisoning with an undefined chemical weapon" was the most likely cause.
The experts said the choice of toxic substance and dose indicates it "most likely was intended to scare the victims, as opposed to cause permanent damage."
Bellingcat said the three men experiencing symptoms consumed only chocolate and water in the hours before the symptoms appeared. It said a fourth member of the team had also consumed the same but did not experience symptoms.
It was not clear who was behind the suspected poisoning, WSJ said, but those targeted blamed hardliners in Moscow seeking to disrupt the negotiations.
Asked Monday about the report, Ukrainian negotiator Mykhailo Podolyak did not confirm the attack. "There is a lot of speculation about the information in the media and various conspiracy theories," he said.
Umerov, who was identified as one of the targets of the suspected poisoning in the WSJ report, urged people not to trust "unverified information."
A U.S. official told Reuters on Monday that intelligence suggested an environmental factor, not poison, made the three men ill. The official, who was speaking on condition of anonymity, did not give reasons for the assessment.
The Kremlin has not commented on the report.
Abramovich is a billionaire Russian businessman with close ties to Russian President Vladimir Putin and one of numerous oligarchs under sanctions from Western countries.
Last week, WSJ reported that Ukrainian President Volodymyr Zelenskyy asked U.S. President Joe Biden not to include Abramovich in U.S. sanctions, arguing that the Russian could help to negotiate a peace deal.
Some information in this report came from Reuters and Agence France-Presse.