The mother of Russian opposition leader Alexei Navalny has filed a lawsuit at a court in the Arctic city of Salekhard contesting officials’ refusal to release her son’s body, Russia’s state news agency Tass reported Wednesday. A closed-door hearing has been scheduled for March 4, the report said, quoting court officials.

Lyudmila Navalnaya has been trying to retrieve her son’s body since Saturday, following his death in a penal colony in Russia’s far north a day earlier. She has been unable to find out where his body is being held, Navalny’s team reported.