Ukrainska Pravda, a Ukrainian news site, reported that several other employees in the agency were also exposed to the poisoning but did not exhibit symptoms.
The Ukrainian media outlet Babel also reported that an investigation was underway into who may have targeted Budanova.
Heavy metal poisoning could refer to substances such as mercury or arsenic. Exposure can cause symptoms such as vomiting, fever and life-threatening organ failure.
Russia and Ukraine have carried out targeted killings of adversaries. Several Russian political opposition figures, including Alexei Navalny, have fallen gravely ill after apparent poisoning, allegedly by an assassination squad within the Russian Federal Security Service, or FSB.
Ukraine’s domestic security service, the SBU, has carried out covert attacks on key figures inside Russia, including a car bomb that killed Daria Dugina, the adult daughter of the Russian nationalist Alexander Dugin.
Budanov has reportedly survived at least 10 assassination attempts, including one attempted car bombing. His wife, who was educated as a psychologist and previously worked for Kyiv Mayor Vitali Klitschko, moved into his office when the war began.
Budanov famously correctly predicted Russia’s full-scale invasion, including plans to capture Kyiv.
Some 21 months later, he and his wife are believed to still live in his office — even with the capital generally safe and most active fighting now occurring in the country’s south and east.
Some of the most pitched battles are underway in the Kharkiv region, near the once occupied town of Kupyansk.
Other fighting is unfolding in the eastern town of Avdiivka, where Russia sent a massive number of soldiers in recent months in a push to seize more land from Ukrainian forces.
The British Defense Ministry said in an intelligence brief this week that Russian forces have suffered thousands of casualties in the process.
Meanwhile, Finland announced on Tuesday that it would close its last remaining border crossing with Russia overnight Wednesday into Thursday after a wave of migrants crossed in recent days in what the interior ministry described as “a Russian hybrid operation.”
“This is a matter of national security,” Interior Minister Mari Rantanen said Tuesday. The border will remain closed until Dec. 13.
Morgunov reported from Warsaw.
