On Saturday evening, 26 individuals experienced carbon monoxide poisoning during a dinner at a tent on a campground in Giswil, Switzerland. Seventeen people required hospitalization after several attendees suddenly became unconscious or reported feeling ill. Initial investigations indicated an accumulation of high levels of carbon monoxide, though authorities have not confirmed if heating sources were involved. The case is under investigation by the local police and the Forensic Institute of Zurich, while a significant response from rescue services from seven cantons was mobilized.