JUAB COUNTY (ABC4 News) – The huge fireball that lit up the desert sky Sunday night was part of the cleanup of a train derailment, but it may have made Utah’s air dirtier.

Juab County Undersheriff Brent Pulver says that 11 of the 24 cars that derailed west of Highway 6 near Jericho Saturday morning were tanker cars were full of volatile fuel that was leaking.

“We had nine rail cars full of propane and two rail cars full of biodiesel,” Undersheriff Pulver said in a phone interview Monday. “So you know when you take that into consideration that’s pretty dangerous.” 

With the risk of an accidental explosion near cleanup crews on site they decided to dispose of the fuel by incinerating it. Sunday night at 9:30 they detonated small charges to open the tankers and then ignited the contents. Undersheriff Pulver was watching from approximately one mile away.

“It was loud. It was bright and it was big,” Undersheriff Pulver said. “It was quite impressive and you know it was a lot bigger than I anticipated.”

The fireball sent a huge plume of thick black smoke into the night sky, concerning to Dr. Brian Moench of Utah Physicians for a Healthy Environment.

“That huge fireball that they created, created an enormous plume of very toxic pollution,” Dr. Moench told ABC4 News. “There was some real toxic substances undoubtedly in that big plume of smoke things like polycyclic aromatic hydrocarbons. Probably a similar sort of mixture as what you would expect to see from an explosion at one of our refineries.”

The ABC4 Pinpoint Weather Computer shows that there were light winds from the north at the time of the explosion that would have dispersed the airborne chemicals to the south. We don’t know the effects of the pollution because the nearest air quality monitor is 50 miles to the northeast in Spanish Fork. Representatives from the Environmental Protection Agency oversaw the operation. 

“We had two individuals from the EPA who were on site. They were monitoring things. It really wasn’t a concern,” Undersheriff Pulver said. “There really wasn’t much other choice. It had to be disposed of.”

Officials expect the cleanup effort to last several more days before the rail line can be reopened.