The Kremlin brushed off allegations Tuesday that Russian opposition leader Alexei Navalny was the victim of an intentional poisoning orchestrated by authorities and said there were no grounds for a criminal investigation so far since it hasn’t been fully established what caused the politician to fall into a coma.

The insistence by the Russian government that Navalny wasn’t necessarily poisoned — comments amplified by Russian doctors and pro-Kremlin media — came a day after doctors at a German hospital where the 44-year-old is being treated said tests indicated he was poisoned.

Moscow’s dismissals elicited outrage from Navalny’s allies, who say the Kremlin was behind the illness of its most prominent critic.

Kremlin spokesman Dmitry Peskov said the accusations against the government “absolutely cannot be true and are rather an empty noise.”

“We do not intend to take it seriously,” Peskov said.

Peskov said he saw no grounds for launching a criminal investigation at this stage, saying that Navalny’s condition could have been triggered by a variety of causes and determining what it was should come before such a proble..

“If a substance (that caused the condition) is found, and if it is determined that it is poisoning, then there will be a reason for an investigation,” Peskov said.

Navalny, a politician and corruption investigator who is one of Putin’s fiercest critics, fell ill on a flight back to Moscow from Siberia on Thursday and was taken to a hospital in the city of Omsk after the plane made an emergency landing.

Over the weekend, he was transferred to the Charité hospital in Berlin, where doctors on Monday said they have found indications of “cholinesterase inhibitors” in his system.

These act by blocking the breakdown of a key chemical in the body, acetycholine, that transmits signals between nerve cells. Navalny is being treated with the antidote atropine.

Navalny’s wife, Yulia Navalnaya, has been visiting her husband daily and made no comment to reporters as she arrived Tuesday.

Chancellor Angela Merkel personally offered Germany’s help in treating Navalny and has called for a full Russian investigation — a sentiment echoed Tuesday by officials from the United States, France and Norway.

U.S. Secretary of State Mike Pompeo said that if reports about Navalny’s poisoning “prove accurate, the United States supports the EU’s call for a comprehensive investigation and stands ready to assist in that effort.”

In response to statements from European officials, the speaker of the State Duma, Russia’s lower parliament house, charged Tuesday that Navalny’s condition could have resulted from a Western plot.

Duma speaker Vyacheslav Volodin in tasked lawmakers to look into what happened to Navalny to make sure it wasn’t “an attempt by foreign states to inflict harm on the health of a Russian citizen and create tension in Russia” in order to ”come up with more accusations” against the country.

Charité said Monday that Navalny had undergone extensive examination by a team of physicians and that “clinical findings indicate poisoning with a substance from the group of cholinesterase inhibitors.”

That covers a broad range of substances that are found in several drugs, but also in pesticides and nerve agents. Charité said the specific substance to which Navalny was exposed isn’t yet known but that a further series of comprehensive tests had been started.

The suggestion that Navalny was poisoned has been vehemently rejected in Russia, where a number of Kremlin critics fell victims to suspected poisonings in recent years, since last week. Government officials, medical specialists and state-controlled media offered a variety of possible explanations for Navalny’s condition.

Doctors in Omsk, a city in Siberia where Navalny was first hospitalized, ruled out poisoning as a diagnosis 24 hours after the politician was admitted and said “a metabolic disorder” was a likely diagnosis.

The editor-in-chief of the RT state-funded TV channel, Margarita Simonyan, speculated that the politician must have suffered from a sharp drop in blood sugar. Some pro-Kremlin news outlets alleged that Navalny mixed moonshine with sleeping pills.

The Charité statement on Monday prompted another array of denials.

The chief intensivist with Russia’s Heath Ministry, Igor Molchanov, questioned whether detecting “substances affecting cholinesterase” five days after Navalny fell ill was at all possible.

Doctors in Omsk said they tested the politician for cholinesterase inhibitors and didn’t find any.

Peskov said Tuesday that specialists in Omsk noted “lowered levels of cholinesterase” — an obstruction of cholinesterase enzymes can be detected by blood tests, experts say — in his body in a matter of “hours” after he was brought in, but that it could have been triggered by a number of causes, including by “taking various medications.”

Navalny’s spokeswoman, Kira Yarmysh, on Tuesday said the government’s reluctance to launch an investigation was expected.

“It was obvious that the crime would not be properly investigated and a culprit found. However, we all know perfectly well who that is,” Yarmysh tweeted.

Western experts have cautioned that it is far too early to draw any conclusions about how the agent may have entered Navalny’s system, but note that Novichok, the Soviet-era nerve agent used to poison former Russian spy Sergei Skripal and his daughter in Britain, was a cholinesterase inhibitor.

“Cholinesterase inhibitor poisons can be given in many ways, they can be transported in many forms, and are very potent,” said Dr. Richard Parsons, a senior lecturer in biochemical toxicology at King’s College London. “This is why they are a favored method of poisoning people.”

Dr. Thomas Hartung, of the Johns Hopkins Bloomberg School of Public Health in Maryland, said such substances are easy to detect, even days and weeks after the poisoning, and that “we will know soon which substance was used.”

“The Novichok nerve agents, used in the 2018 poisoning of the Russian double agent Skripal in England, also belong to this category of substance,” he said. “I said at the time that the Russians could have have just left a business card at the crime scene, because the substances can be so clearly traced.”

(AP)