Sept. 17 (UPI) -- Russian opposition leader Alexei Navalny, who died in a Russian prison last year, was poisoned, said his widow, Yulia Navalnaya, on Wednesday.

Navalnaya showed images of his prison cell showing vomit on the floor the day he died. She also showed video excerpts from a court date just days before his death in which he looked healthy. But at the end of the 15-minute video, she said her team had obtained smuggled biological samples from Navalny's body, and two independent labs had determined that he was poisoned.

Navalny died while in prison in February 2024, and Russian authorities said he died of natural causes. He had been held in a penal colony near Salekhard, a city above the Arctic Circle located more than 1,900 miles northeast of Moscow. He ran for president in 2018 against Vladimir Putin and had a strong following throughout the country and admirers around the world.

"Labs in at least two countries examined these samples independently of each other. And these laboratories, in two different countries, reached the same conclusion: Alexei was killed -- more specifically, he was poisoned."

She didn't say which poison was found and didn't give many details. Her team told CNN that part of the reason she made the video was to pressure the labs to release the results. They also wouldn't confirm which countries the labs were in.