MARYVILLE, Tenn. — A CSX train car carrying hazardous material derailed and caught fire in the middle of the night in eastern Tennessee, forcing the evacuation of thousands of people and sending dozens to the hospital with respiratory issues and nausea.

The fire was still burning around noon Thursday, and officials said firefighters had been unable to get close to the burning car because of the heat. Blount County Mayor Ed Mitchell said there were also concerns that the fumes contained cyanide, a byproduct of burning the chemical acrylonitrile, which was leaking from the train car. The smoke had stopped by 6 p.m., however, Mitchell said.

About 5,000 people in the area were being evacuated, along with several businesses. A manufacturing plant, Denso Manufacturing, closed down Thursday morning because of its proximity to the derailment, Blount County firefighter Kermit Easterling said.

Officials said firefighters had been trying to hose down neighboring rail cars and keep them cool while also trying to move them away from the flames.

The damaged car was carrying liquid acrylonitrile, which officials said is a hazardous material used in multiple industrial processes including making plastics. It's flammable and it's dangerous if inhaled. The EPA says some effects of breathing acrylonitrile include headaches, dizziness, irritability and rapid heartbeat.

Fifty-two people were treated at Blount Memorial Hospital in Maryville, and 25 were admitted, hospital spokesman Josh West said. None had life-threatening injuries, but were experiencing respiratory issues, skin irritation and nausea, West said.

Ten first responders were treated at the hospital after breathing fumes.

CSX regional vice president for state government affairs Craig Camuso said authorities didn't know how much acrylonitrile was spewing out and burning, or how much remained in the tank.

The fire was reported shortly before midnight Wednesday.

Mitchell asked residents near the derailment site not to drink well water for now. He said CSX would provide bottled water to residents at a local middle school, even though city officials said there was no indication yet whether well water was been affected by the accident.

Kevin Eichinger, an on-scene coordinator with the EPA, said air, water and soil samples would be tested. He said early air testing Thursday indicated air quality "around background levels."

Maryville City Manager Greg McClain told evacuees to plan to be away from home at least Thursday night.

"We're doing our very best to get you back to your homes as soon as possible," he said.

Camuso said the company was putting people up in hotels, and would give them gift cards for food and essentials.

"We will continue to do that for as long as it takes," he said.

The train was traveling from Cincinnati to Waycross, Georgia.

Camuso said it had 57 cars and two locomotives, and that 27 cars carried hazardous chemicals: nine with acrylonitrile, 16 with propane and two with asphalt. He said the cause of the derailment is not yet known.

The Federal Railroad Administration said it had investigators and hazmat inspectors at the scene, and would investigate the cause once it's safe.

The National Transportation Safety Board is not investigating the accident, but will monitor it and could send an investigator later, NTSB spokesman Terry Williams said in an email.

In general, the transportation of hazardous materials in commerce is regulated by federal law, which requires that hazmat shippers be registered, the material be properly classified, the handlers have preliminary hazmat training and that the material be labeled and held in proper containers, Pipeline and Hazardous Materials Safety Administration spokesman Gordon "Joe" Delcambre Jr. said in an email.

He said more than 1 million daily shipments of hazardous materials are moved across the nation by all modes of transportation.

A shelter for residents was set up at a local high school. Several residents there said they were not aware of the derailment until they got a call or someone knocked on their door early in the morning.

"We saw police going back and forth and emergency vehicles going back and forth on our road, but we didn't know why until about 3 to 3:30," Maryville resident John Trull said. "That's when they told us. We didn't hear anything (beforehand). We just saw some emergency vehicles go by and kind of wondered what was going on, and that's about it."

Brittany Parrott said she was awakened by a knock on her apartment door about 4:30 a.m. Although she didn't hear the derailment, she said she noticed the effects of it as she went outside.

"You could smell it in the air," Parrott said. "I had a headache, I was feeling nauseated and lightheaded, all the symptoms."

Maryville is a town of nearly 30,000 people located about 20 miles south of Knoxville and just outside the Great Smoky Mountains National Park.