Members of six participating teams — Finland, Greece, Lithuania, Slovenia, Spain and Turkey — staying in the same hotel in Nis, Serbia, had shown symptoms of illness including nausea, fever, abdominal pain and diarrhea since Monday, the cause of which is still unknown. Multiple players spent the night in a hospital, sources told ESPN.

The affected teams were given the option to postpone Wednesday’s games by FIBA officials but declined, FIBA said.

“Some of the teams’ personnel continue to be weakened by the illness but the majority of those affected have either recovered or on their way to full recovery,” FIBA said in its statement. “The Serbian Basketball Federation are waiting for the official results of the tests conducted by the relevant health authorities investigating the exact cause of the illness.”

The tournament has been marred by issues since the opening day, when slippery floors caused multiple injuries and an unusual protest as players refused to meaningfully contest the final five minutes of a game due to poor playing conditions.

One player affected by the floor conditions, Polish forward Jakub Szumert, was ruled out of the remainder of the tournament after experiencing breathing difficulties during practice, his agent Grzegorz Kulig told ESPN. Szumert is in stable condition but will leave Serbia to receive treatment in his native Poland, Kulig said.

Szumert lost his balance pursuing a loose ball on the wet court in the Mika Antic elementary school gym and landed violently on his chest Saturday. While making his way to his team’s bench, he fainted, lost consciousness and experienced breathing difficulties and was later rushed in an ambulance to a local hospital where he spent the night. Szumert was again sent to the hospital Wednesday but was cleared by doctors, Kulig said.

Jonathan Givony is an NBA draft expert and the founder and co-owner of DraftExpress.com, a private scouting and analytics service used by NBA, NCAA and international teams.