MOSCOW — Colleagues of Russian opposition leader Alexei Navalny said Thursday that a water bottle with a trace of the Novichok nerve agent was found in his hotel room in the Siberian city of Tomsk after he fell ill on a flight from there to Moscow last month.

Navalny later was flown to Germany, where he was kept in an induced coma for more than two weeks as he was treated with an antidote at Berlin’s Charite hospital.

Members of his team accused the Kremlin of involvement in the poisoning, charges that Russian officials have vehemently denied.

The Kremlin has bristled at calls from German Chancellor Angela Merkel and other leaders to answer questions about the poisoning, urging Germany to provide its evidence.

On Tuesday, Navalny posted a picture of himself from his hospital bed, hugged by his wife and children. “I still can’t do almost anything on my own, but yesterday I managed to breathe on my own for the entire day,” he added in the post.

A video posted on Navalny’s Instagram account on Thursday showed members of his team in plastic gloves inspecting his hotel room in Tomsk shortly after he left the city on Aug. 20 and collapsed on a flight home.

The plane made an emergency landing in Omsk, where he was hospitalized before being taken to Berlin two days later on a medevac plane.

Navalny’s Instagram post said they went to the room an hour after learning that he had fallen ill, accompanied by a lawyer, and packed half-empty plastic water bottles and unspecified other items for further inspection. In the video post, someone who appears to be a hotel employee could be heard telling members of the Navalny team that they need to ask police before taking any items from the room, and one of them refuses to do that.

“Two weeks later, a German laboratory found a trace of Novichok on a bottle from the Tomsk hotel room,” they said. “And then another three labs that took Alexei’s samples proved that he was poisoned with it.

Now we understand: It was done before he left his room to go to the airport.”

There had been previous speculation that Navalny was poisoned at the airport, where he drank a cup of tea before boarding the flight.