Yulia Navalnaya, the widow of late Russian opposition leader Alexei Navalny, said Wednesday that foreign laboratory tests on biological samples obtained from her husband confirmed he was poisoned.

“A year and a half ago I promised you we were doing everything to investigate Alexei’s murder … We collect every scrap of information,” Navalnaya said in a video.

“Back in February 2024, we were able to obtain and securely transfer abroad biological samples of Alexei. Laboratories in two countries independently tested those samples. These labs in two different countries reached the same conclusion: Alexei was killed. More specifically, he was poisoned,” she said.

Navalny, 47, died suddenly in February 2024 in prison above the Arctic Circle, depriving Russia’s opposition of its most charismatic leader. He had been serving a sentence of more than 30 years behind bars on charges that he and the EU denounced as politically motivated to suppress his criticism of Russian President Vladimir Putin.

For nearly a decade, Navalny was Putin’s most persistent domestic critic. In August 2020, he was put into a medically induced coma after being poisoned with the nerve agent Novichok — an attack his supporters allege was sponsored by the Kremlin. He recovered in Germany, but when he returned to Moscow in 2021, authorities immediately arrested him.

Last year, Navalnaya rejected Russian investigators’ claims that Navalny died from a “combination of diseases,” insisting she would push for a criminal investigation into what she considers her husband’s murder, while his team would continue to conduct its own independent inquiry.

Top European officials said they considered Putin directly responsible for Navalny’s death. The AP and The Wall Street Journal last year cited anonymous U.S. intelligence sources as saying there was no smoking gun pointing to Putin’s direct involvement in Navalny’s death, though they did not dispute he was ultimately responsible.

Navalnaya repeated Wednesday that she considered Putin to be responsible for her husband’s death and demanded the laboratories release their findings regarding what she called the “inconvenient truth.”

“These results are of public importance and must be published. We all deserve to know the truth,” she said.