The fire was limited to the first floor, although the burning material created toxic fumes and smoke, which ascended throughout the hotel tower via vertical shafts (elevators and stairwells) and seismic joints, causing the majority of the deaths. Firefighters reported having to crawl through the dark and over "mounds of stuff" trying to extinguish the fire, it was later determined that the "mounds" were deceased guests and staff near an elevator bank. The Las Vegas fire department operated separately from the county fire department; the latter served the Las Vegas Strip, so city firefighters were unfamiliar with the MGM's layout, including fire escape routes. This hindered the rescue effort.