Russian oligarch Roman Abramovich and multiple Ukrainian peace negotiators suffered from symptoms of what is suspected to be a poisoning attack following a meeting in Kyiv earlier this month, The Wall Street Journal reports per people familar with the situation.

Afer the meeting, Abramovich and at least two senior members of the Ukrainian team “developed symptoms that included red eyes, constant and painful tearing, and peeling skin on their faces and hands,” the Journal writes. Sources blamed the presumed poisoning on “hard-liners” in Russia hoping to sabotage peace negotiations. A person close to Abramovich said the perpetrator is unclear.

Those affected have since improved and their lives are not in danger, the sources told the Journal. A spokesperson for Ukrainian President Volodymyr Zelensky did not have any information to add.

Western experts who looked into what happened “said it was hard to determine whether the symptoms were caused by a chemical or biological agent or by some sort of electromagnetic-radiation attack,” the Journal writes.

The incident “was not intended to kill,” however; rather, “it was just a warning,” said German investigator Christo Grozev, who was eventually able to examine a sample.

Abramovich has apparently decided to remain in negotiations, of which he’s been an active part, despite what happened. He became involved in peace efforts shortly after Russia President Vladimir Putin’s invasion initially began, the Journal notes.

Abramovich is one of Russia’s wealthiest men, and also the owner of London’s Chelsea Football Club. Read more at The Wall Street Journal.