Several train cars carrying volatile chemicals derailed and exploded Tuesday south of Louisville, shutting down a highway and forcing evacuations of homes, businesses and a school, authorities said.

No serious injuries were reported, but at least 11 people near the crash checked themselves into a hospital and were soon released, authorities said. Officials asked residents within a mile to evacuate.

The blaze produced a large column of black smoke in the mostly rural area. Television footage showed several blazing cars stacked across the rail lines and flaming liquid flowing down ditches from the mangled tanker cars.

The fire continued into Tuesday evening, and officials said they will likely have to let the chemicals burn themselves out.

The chemicals on the CSX train contributing to the fire were cyclohexane, methyl ethyl ketone, butadiene and alcohol, said Gary Sease, a CSX spokesman.

"These substances themselves are pretty toxic, but when they burn they break down a whole lot," said Jeremey Urekew, a spokesman for Bullitt County Emergency Management. "This fire is going to burn itself out."

Two other cars were carrying hazardous materials that could pose an environmental threat, but they were not near the fire, he said.

Sease said the train — with four locomotives and 80 cars — was headed to Louisville from Birmingham, Ala.

The immediate area, including Brooks Elementary School, was evacuated, said state police Maj. Lisa Rudzinsky.

The crash occurred about 8:45 a.m. EST, and an 18-mile stretch of Interstate 65 remained closed into Tuesday evening.

The Kentucky National Guard said it mobilized 20 to 25 soldiers and airmen to check air quality.

Bullitt County resident Daymon Strange said he was outside his home less than a half-mile from the crash site when he heard an explosion.

"I turned around and looked and there was fire at least 500 feet in the air," he said in a telephone interview. "I've never seen such a fire. It was huge."

Strange said he smelled the fumes even though they were blowing away from his home.

"You can taste it and feel it in your lungs when you go outside," he said.

The Red Cross set up a shelter in neighboring Jefferson County for evacuees, but only about a dozen people had checked in by early evening, said William Ney, a volunteer.

Officials with the National Transportation and Safety Board were investigating and declined to comment on a possible cause.

Gov. Ernie Fletcher, who flew over the area with the Kentucky Air National Guard, said he has not determined whether a state of emergency will be declared.

It was the second fiery train crash in Kentucky in two days. On Monday, four runaway rail cars struck two parked locomotives in central Kentucky, catching fire and spilling a chemical that prompted a limited evacuation.