An illness has affected a number of attendees at Portugal's Waking Life festival. The exact cause is not yet known, but it's left some festivalgoers vomiting and suffering diarrhoea. "At the moment we are trying to figure out the exact source of the illness that has been going around," the festival said in a Facebook statement. "What we are sure of is that it is not the tap water which we are using since July 1st for all food preparations and drinking. Also the lake water has been tested and proven to be safe. We are aware that throughout the festival some of our medical staff have been spreading that the tap water was not drinkable. However, this was based on nothing but an assumption. Later the head of the medical team apologised for this misinformation." One festival attendee, who was not affected by the illness but had friends who were, told Resident Advisor: "We had to stop the car on the way to the airport and we had to stop every ten minutes for them to get out and vomit." Others wrote in the comments section below the festival's statement. "Besides the inconvenience of the illness itself, my friend and I also had to miss/rebook our flights causing significant financial harm," one attendee wrote. "I'm sick right now, but I'll come back next year," said another. Festival organisers are telling those affected to "take something for the stomach, hydration sachets and eat healthy. It should fix you in about a day or two." They add: "Doing something for the first time always comes with many learnings. After a thorough evaluation and self assessment we will write a full report on the positive and negative, which will be published on our website. We are happy to receive any constructive ideas and suggestions."