(NewsNation) — Russian oligarch Roman Abramovich and Ukrainian officials he had been conferring with as part of peace talks between Russia and Ukraine reportedly developed symptoms of poisoning following meetings earlier this month.

Abramovich, who had accepted a Ukrainian request to help negotiate an end to the war and at least two senior members of the Ukrainian team developed symptoms including peeling skin and red eyes. The symptoms were first reported by The Wall Street Journal on Monday, citing people familiar with the matter.

Tracy Walder, a former CIA officer, suggested that Russian leader Vladmir Putin may be responsible.

“I think that something like this, in my opinion, would have absolutely come, come from Putin himself,” he said Monday on NewsNation PRIME.

An anonymous U.S. official disputed the notion that poisoning was responsible for the symptoms, instead citing environmental factors. Ukrainian officials were similarly dismissive. Rustem Umerov, who serves on the Ukrainian negotiating team, suggested the public shouldn’t trust “unverified information.” Ukrainian Foreign Minister Dmytro Kuleba was similarly dismissive but also added a joke, saying that he advises “anyone going for negotiations with Russia not to eat or drink anything, (and) preferably avoid touching surfaces.”

The Russian state has long been suspected of using poison against its opponents. For instance, in 2006, Russian defector Alexander Litvinenko died three weeks after his green tea was poisoned in London with radioactive polonium. The European Court of Human Rights later ruled that Russia was responsible for what it called the “assassination” of Litvinenko.

Former Ukrainian President Viktor Yuschenko was poisoned with dioxin, a chemical found in Agent Orange, in 2004. Although there is no definitive evidence that Russia was behind the poisoning, many have suspected that Moscow was behind the incident, pointing to Yuschenko’s pro-Western political orientation.

Brett Bruen, former director of global engagement at the Obama White House, emphasized Russia’s vast intelligence capabilities.

“There are a lot of intelligence officers, operatives, contacts roaming around these places trying to both gather intelligence but also engage in some of these kinds of shenanigans. And it was par for the course, certainly, with Russia before,” he said Monday as a guest of “On Balance with Leland Vitter.” “I think these days, obviously, with so much on the line for Putin, he is pulling everything and the kitchen sink out.”