It is thought that the fire was started by a discarded match or cigarette. The fire quickly engulfed the canvas "big top" sending patrons scrambling for the exits. Most fatalities were due to severe burns, as the canvas fell onto the crowd, and it is likely that some were due to crushing by the crowd rushing to get out.
All visitors can download an article from the July 1944 edition of NFPA's The Quarterly. The article includes a newspaper article, and recommendations regarding circus fire safety.