The judicial panel will have to be formed again and the hearings will have to start from scratch, Ukrainian UNN news agency reported.
The case was sent for retrial in December 2016 over the new composition of the panel, which began announcing the verdict in February this year.
In 2014, a group of Ukrainian nationalist radicals who were supporters of the newly installed Kiev government, clashed with anti-Kiev protesters in Odessa. Anti-government protesters attempted to hide in Odessa's Trade Unions House, which was then set on fire by Molotov cocktails hurled inside.
The clashes and fire left 48 people, including seven women and one minor, dead while the overall number of casualties exceeded 250, according to the Office of the United Nations High Commissioner for Human Rights (OHCHR). According to media reports, 26 people from both sides currently stand accused in the case. The case has been on trial since November 2014, but hearings have often been rescheduled.