Russian dissident Vladimir Kara-Murza said his mother was in a Berlin hospital on Tuesday, while German police said they were investigating a case of attempted murder.

Kara-Murza said that suspicions that his mother, a German-Russian citizen, was poisoned have not been confirmed.

Police said toxicology test results are not expected until Wednesday.

“My mother is indeed in a hospital in Berlin, but the suspicions of poisoning or a heart attack have fortunately not been confirmed,” Kara-Murza posted on social media. “Doctors are continuing to evaluate.”

He complained of symptoms of poisoning

Police said the woman, whose name was not released, was moved to the isolation wing of Charite Hospital. In the afternoon, she went to the hospital complaining of symptoms of poisoning.

“We are currently investigating whether there is evidence of political motivation,” police spokeswoman Jane Berndt said. She added that the victim’s apartment, in the western district of Charlottenburg-Wilmersdorf, was being searched for clues.

Kara-Murza, a prominent critic of Russian President Vladimir Putin and his all-out invasion of Ukraine, was one of more than 20 prisoners which Russia, Belarus and the West exchanged in August, in the largest prisoner exchange since the Cold War.

Among those he was replaced with is the Russian assassin Vadim Krasikov. convicted of murder in 2019 in the Berlin park of a Georgian citizen who was part of the Chechen independence movement.

Last year, Russian investigative journalist Elena Kostyuchenko fell ill on a train to Berlin after what she believed to be a poison attack. The police opened an investigation into attempted murder.