DUPO, Ill. — Crews are monitoring air quality in Dupo, Illinois, after Tuesday’s train derailment at the Union Pacific yard.

"We've had them before here in this yard but nothing nowhere near this magnitude,” said Herb Simmons, director of the St. Clair County Emergency Management Agency

Union Pacific railroad says during the derailment, a tank carrying a chemical called methyl isobutyl ketone caught fire.

The chemical is used as a solvent, and it's highly flammable. According to the National Institutes of Health, it can cause skin and eye irritation.

RELATED: What is the chemical involved in the Dupo train derailment?

"The EPA is here because some of that got into a drainage ditch and they got that stopped,” Simmons said.

First responders evacuated Dupo schools and three nearby neighborhoods for a few hours until testing showed the air quality was safe. People who needed shelter congregated at East Carondelet Community Center.

"My mother's in there and she has dialysis and she has a nebulizer so I was really worried about the toxicity,” neighbor Debra Schell said.

The St. Clair Emergency Management Agency says the EPA is monitoring the air, and the railroad says its environmental contractor will be doing the same
for at least five miles downwind of the derailment until further notice.

"They won't leave any stones unturned,” Simmons said.

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