After studying footage of the weekend’s Indiana State Fair stage collapse, some experts suspect a “gustnado” caused the deadly accident.
Gustnadoes are defined as ground-based wind vortexes that sometimes form along the front of thunderstorms, MyFoxChicago.com reported Tuesday. While similar to twisters, gustnadoes are much weaker, with winds between 60 to 90 mph.
Senior meteorologist Henry Margusity of AccuWeather.com told Reuters that a gustnado could have pushed already strong winds to gusts of up to 60 mph or more.
"If you analyze the video, you can see that gustnado kind of coming across and moving through, and everything's twirling around as it goes through," Margusity said.
The footage also shows flags changing directions as the wind passed through, another move typical of gustnadoes.
The stage collapsed on screaming spectators, killing five and injuring at least four dozen.
Gustnadoes were spotted and filmed in other parts of Indianapolis just before the accident, but Harold Brooks, a research meteorologist with the U.S. government weather agency NOAA, told Reuters that he didn’t believe that that specific type of wind was involved.
"It's not clear that the winds were very strong," Brooks told Reuters, adding that 40-50 mph thunderstorm winds are not unusual.
Both meteorologists agreed, however, that gustnadoes are rarely deadly, Reuters reported.
Whatever the cause, it’s likely the storm was nearly impossible to prepare for. Indiana Gov. Mitch Daniels called the event a “fluke.”
But questions about whether the fair did enough to anticipate a storm have loomed over the event, with the emergency plan outlining severe weather procedures giving no mention of potential evacuations.
While part of a larger emergency preparedness plan, the severe weather section is only one page long and only gives generic recommendations.
Some fairs hire their own meteorologists for just such a scenario.
Gov. Daniels on Tuesday called the state fair's emergency plan a "pretty well thought-through policy" but did not elaborate. The governor also said he may support mandating limited inspections of temporary structures, like the state fair stage.
It remained unclear Tuesday whether anyone had inspected the stage, or if anyone was supposed to do so.
The Indiana Department of Homeland Security -- which includes the state fire marshal -- said it did not inspect the stage. In years past, a deputy state fire marshal has done site inspections of the fair, including its stages, said the emergency official who spoke anonymously. He was unsure if an inspection was conducted this year.
Klotz has said the fair's executive director and an Indiana state police captain were headed to the stage to order an evacuation when it collapsed.
The Associated Press contributed to this report.