Immediately after Aleksei A. Navalny, Russia’s most prominent opposition leader, showed symptoms of poisoning last month, members of his team rushed to the Siberian hotel where he had been staying and grabbed anything that could possibly be used as evidence — including a water bottle that tests showed was tainted with a highly toxic nerve agent.
Even as Russia maintains that it played no role in the poisoning of Mr. Navalny, the new details — released on Thursday in a post on Mr. Navalny’s Instagram account — underscore his team’s deep concerns for his well-being and their fears that he could fall victim to the kind of attacks directed at other Kremlin critics.
In a video posted on Instagram, members of Mr. Navalny’s team swiftly donned rubber gloves and scoured his room at the Xander Hotel in Tomsk, packing evidence into blue plastic bags.
The plastic water bottle, Mr. Navalny’s team and German investigators say, eventually helped German military scientists determine that the opposition leader had been poisoned with a class of chemical weapon called a Novichok, a Soviet-designed poison that Russian operatives have used in at least one previous assassination attempt.
The rush to grab evidence suggests that Mr. Navalny and his team had been prepared for the eventuality that there would be an attempt on his life. Indeed, at meetings with supporters around Russia, he was frequently asked how he remained alive, given his vicious criticism of the Kremlin and Russia’s most powerful figures.
His continued existence even fueled conspiracy theories that he was in fact a government puppet, paid to play the role of an opposition figure, while never actually seeking power himself.
On Aug. 20, those doubts were put to rest when Mr. Navalny began choking and screaming on a flight to Moscow from the Siberian city of Tomsk.
Immediately after Mr. Navalny’s plane made an emergency landing, his aides contacted members of the team who had stayed in Tomsk to tell them what had happened, according to Mr. Navalny’s Instagram post.
“At that moment, they did the one thing that was possible,” the statement said. “They called a lawyer, went to the hotel room, which Navalny had just left, and began to identify, record and pack up everything that they found, including bottles of water from the hotel.”
When Mr. Navalny was flown from a Siberian hospital to Berlin on Aug. 22, the evidence went with him. It is unclear how Mr. Navalny’s team was able to sneak the bottle and other items out of the country without the Russian officials knowing.
Russia has insisted since Mr. Navalny first fell ill that he was not poisoned, and has instead offered a number of alternative theories, like he had been using cocaine or that he had low blood sugar and simply needed to eat some candy. Such statements convinced Mr. Navalny’s team that the Russian authorities had no interest in conducting a real investigation.
“It was absolutely clear to us that Navalny was not lightly ill or got overheated and that a Raffaello candy would not help,” the Instagram post read. “So we decided to grab everything that might hypothetically be of use and give that to the doctors in Germany.”
An analysis by German military scientists at the Institute for Pharmacology and Toxicology in Munich found traces of a nerve agent in the Novichok family in Mr. Navalny’s blood and urine, as well as on one of the bottles. Based on the German findings, Mr. Navalny’s team, according to the Instagram post, now believes that he was poisoned in that hotel room, not at the airport as they had originally suspected.
Laboratories in France and Sweden this week confirmed the German findings that Mr. Navalny had been poisoned with a nerve agent from the Novichok family. A similar poison was used by Russian military intelligence operatives who traveled to Britain in 2018 to attack Sergei V. Skripal, a former intelligence officer who had served prison time in Russia for spying for the British before being traded in a spy swap.
Given the substance used, the German authorities and others say there is no doubt that the Russian government was behind the poisoning, a breach of the Chemical Weapons Convention to which it is a signatory.
The Organization for the Prohibition of Chemical Weapons, the world’s chemical weapons watchdog, is expected to release in the coming days the results of its own analysis of biomedical samples collected from Mr. Navalny by its team of experts, the agency said in a statement on Thursday.
If those results confirm the German, French and Swedish findings, the German government would move quickly to impose financial sanctions on Russia through the European Union, according to a senior German security official, who spoke on condition of anonymity to discuss internal deliberations.
“We don’t doubt our own result,” the official said. “It’s just to give it even more political legitimacy.”