The German government has said specialist laboratories in France and Sweden have confirmed Russian opposition leader Alexei Navalny was poisoned with the Soviet-era nerve agent Novichok.
A German military laboratory previously confirmed the substance was present in his samples.
German government spokesman Steffen Seibert said the Organisation for the Prohibition of Chemical Weapons has also received samples and is taking steps to have those tested at its reference laboratories.
Nerve agent Novichok was used to poison Russian opposition leader Alexei Navalny, a move Chancellor Angela Merkel called "attempted murder".
Mr Navalny, a politician and corruption investigator who is one of Russian President Vladimir Putin’s fiercest critics, fell ill on a flight back to Moscow from Siberia on August 20.
He was taken to hospital in the Siberian city of Omsk after the plane made an emergency landing.
He was later transferred to Berlin’s Charite hospital, where doctors earlier this month said there were indications he had been poisoned.
Earlier this month, Novichok poisoning survivor Charlie Rowley told ITV News the chemical attack on Mr Navalny has "given Russia some strength to carry on and get away with it".
Mr Rowley told ITV News: "I felt devastated the fact that it happened again, I thought it was over but it clearly isn't.
"I think it gives the Russians some strength that they can carry on with their business and get away with it."
His partner, Dawn Sturgess, died after being exposed to the nerve agent in July 2018, following the attack on former Russian spy Sergei Skripal and his daughter Yulia in Salisbury in March that year.
Ms Sturgess was exposed to the nerve agent when Mr Rowley presented her with a perfume bottle he had found, thinking it was a brand of designer fragrance.
Mr Rowley survived coming in to contact with the chemical weapons, although it has had a lasting impact on his health.
Even after two years, he said he is "still left with problems with my eyesight in my right eye, I get out of breath and suffer from depression".