More than a dozen people were injured Sunday afternoon after authorities responded to a call about an odor of gas inside a building with people passing out. According to the Marshalltown Fire Department, firefighters, law enforcement and UnityPoint Health-Marshalltown EMS officials responded to 305 E. South St., where upon arrival, police officers found people inside the building with complaints ranging from difficulty breathing to headaches. Authorities immediately began removing people from the building. On arrival of MFD crews, the remaining victims were also removed from the building. An initial test of the air inside the building found a high concentration of carbon monoxide. In total, 15 victims were transported to the local hospital. Inside the building, MFD crews found a gasoline-powered generator in the basement that had been running to provide light and heat in the building. In addition, numerous gasoline cans were found that contained gasoline. Alliant Energy was called to the scene, but no electric or gas service was present in the building. Of the victims transported to Unity Point-Marshalltown, five were later airlifted via helicopter and three transported by ambulance to facilities in Iowa City and Des Moines.