German doctors treating Pyotr Verzilov, a member of Russian protest group Pussy Riot, say claims that he was poisoned are "highly plausible," based on his symptoms.
Dr Karl Max Einhaeupl of Berlin's Charite hospital told reporters Tuesday there is no evidence Verzilov was suffering from a long-term illness.
His colleague Dr Kai-Uwe Eckardt said Verzilov, who has Canadian citizenship, has been receiving intensive care since arriving in Berlin on Saturday but his condition isn't life threatening.
Eckardt said Verzilov was treated well in Moscow before being flown to Germany. He says the symptoms indicate a disruption of the part of Verzilov's nervous system that regulates the inner organs.
Doctors in Berlin haven't yet determined what substance was responsible for the poisoning.