Russian investigators will consider whether someone tried to assassinate opposition leader Alexej Navalny.
The Russian investigation committee has asked its department in Siberia for further investigation, the Russian news agency RIA reports.
Kremlin critic Navalny became very ill on board a flight from Siberian Tomsk at the end of August. According to people close to him, he may have been drinking poisoned tea.
According to Russian medics, no poison had been found in the blood or urine of Navalny, who is said to suffer from a rare metabolic disorder.
Navalny was later transferred to a hospital in Germany. The German government reported on Wednesday that it had “unambiguous evidence” that Navalny had been poisoned with a nerve agent from the Novichok group.
Josep Borrel, the European Union’s foreign chief, on Thursday evening called for a “joint international response” to the assassination attempt, leaving open the option of new sanctions against Russia. “Impunity should not and will not be tolerated,” said Borrell.
NATO countries will address the issue on Friday.