A team-building exercise in Switzerland did not work out as planned when 25 employees suffered burns after walking over a bed of coals that stretched several feet long, New York Post reports. 

At least 10 ambulances arrived at a private event on the Au peninsula on Lake Zurich Tuesday night to provide medical treatment, with 13 people transported to a nearby hospital with severe injuries. Police have begun an investigation into the incident and gathered evidence from the site. It’s uncertain if the arrangement of the coals or the way the participants walked over them contributed to their injuries.