Sixteen people, including children, fell ill Thursday afternoon at the AVA Thermalpark in Diakovce, Slovakia, after exposure to an unidentified substance. Half of those affected required hospitalization. Firefighters conducted tests at the water park, but found no elevated chlorine levels, ruling out that as the immediate cause. The substance responsible for the illnesses remains unknown as of Friday. Police have launched a criminal investigation to determine the source of the contamination and the cause of the mass poisoning. Authorities are working to identify the substance and ensure the safety of the public. The incident has raised concerns about safety protocols at the thermal park.