Navalny died from 'sudden death syndrome,' the prison told his mother

Russian opposition leader Alexei Navalny's mother was told over the weekend her son died from "sudden death syndrome" and that his body will not be given to the family until an investigation is complete, according to the director of Navalny's Anti-Corruption Foundation.

Navalny, who rose to prominence for his campaign against corruption and Russian President Vladimir Putin, died in a remote Arctic penal colony last Friday at the age of 47, Russian prison officials confirmed.

The Russian Federal Prison Service said Navalny felt unwell after a walk and lost consciousness. An ambulance was called and crews tried to rehabilitate him, but they were unsuccessful. He was serving a 19-year sentence on charges of extremism and had recently moved from a different prison to the country's highest security level facility near the Arctic Circle.

Navalny's mother, Lyudmila, on Saturday visited the penal colony where her son died and received an official death note that stated his time of death as 2:17 p.m. local time on Feb. 16, his spokesperson, Kira Yarmysh, wrote on X, the platform formerly known as Twitter.

"When Alexei's lawyer and mother arrived at the colony this morning, they were told that the cause of Navalny's death was sudden death syndrome," Ivan Zhdanov, the director of Navalny's Anti-Corruption Foundation, wrote Saturday on X.

"Sudden death syndrome" is a general, vague term used to describe various cardiac syndromes that can prompt sudden cardiac arrest and death.

Yarmysh on Saturday said an employee of the colony said Navalny's body was picked up by investigators from a Russian intelligence agency and brought to Salekhard, a Russian town about 30 miles south of Kharp, where Navalny died in prison.

When his mother and lawyer arrived at the morgue in Salekhard on Saturday, it was closed, Yarmysh said on X.

"It's closed, however, the colony has assured them it's working and Navalny's body is there," she wrote. "The lawyer called the phone number which was on the door. He was told he was the seventh caller today. Alexey's body is not in the morgue."

Navalny's team was initially informed Saturday that no traces of criminality were discovered, Reuters reported. One of his lawyers, however, was later informed by Salekhard's Investigative Committee that the cause of his death had not yet been established and a new histological examination was carried out, per Yarmysh. The committee confirmed Navalny's body will not be handed over to relatives until the investigation is complete, she added.

"Right now we don't have access to the body, and we don't know for sure where it is, and we demand that the Russian authorities immediately give Alexei's body to his family," Yarmysh said in an interview with Reuters on Saturday.

Navalny's death prompted scrutiny of Russia from around the world, with several world leaders pinning the blame on Putin, who has not commented on Navalny's death.

The Kremlin called the West's reaction unacceptable and "absolutely rabid," per Reuters.

Navalny had been imprisoned since 2021, when he came back to Russia after recovering from a poisoning that he blamed on Putin. The Russian president has denied his allegations.