CHRISTOPHER, Ill.  — A Union Pacific freight train derailed near this southern Illinois community early Monday, spilling an unknown chemical and leading to the evacuation of more than 70 homes.

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Two locomotives and 21 cars of the 83-car train left the tracks around 2:35 a.m., Union Pacific spokesman James Barnes said. The train was headed to Chicago from Houston.

About a dozen people were taken to hospitals for treatment of mild symptoms, including burning or irritation of the throat, eyes and nose, said Tracey Karnes, a spokeswoman for Benton-based ambulance provider Mercy Regional Health Services.

The victims included residents and emergency responders. Karnes didn’t think any injuries were serious enough to require hospitalization.

Barnes said railroad officials were still trying to determine what chemical had leaked.

The cause of the derailment had not been determined, authorities said.

A hazardous material team was on the scene of the derailment, said John Hampton, a West Frankfort police and fire dispatcher.

More than 70 homes in the area of Mitchell Lake were evacuated, Barnes said.

Christopher is a town of 2,800 located about 20 miles north of Carbondale.