Thousands of people were evacuated on Wednesday night in eastern Tennessee after a freight train carrying a flammable and toxic substance derailed and caught fire, the Associated Press reported.

Operator CSX said the train was carrying acrylonitrile, a hazardous material used in a variety of industrial processes, including making plastics. The substance is flammable and can be dangerous if inhaled, the company explained in a statement; the Federal Railroad Administration dispatched investigators and hazmat inspectors to the scene, the AP noted.

Effects of ingesting acrylonitrile can include headaches, dizziness, irritability and rapid heartbeat, according to the federal Environmental Protection Agency, and seven local law-enforcement officers were hospitalized after breathing in fumes, Blount County Sheriff's Department spokeswoman Marian O'Briant told NBC News.

"Cars of acrylonitrile are located on either side of the burning rail car," CSX spokeswoman Kristin Seay noted. "CSX personnel are on hand at an outreach center that has been established. Displaced residents are being offered assistance, including lodging," she added.

The train had been traveling from Cincinnati to Waycross, Georgia, and consisted of two locomotives, 45 loaded rail cars carrying mixed freight, and 12 empty rail cars, Seay summarized.

The Blount County Fire Department in Maryville, Tennessee, a community of about 27,000 inhabitants, was notified of the derailment around 11:50 p.m. on Wednesday night, Lt. Johnny Leatherwood told the AP; by 8:15 a.m. on Thursday, the train was still burning, firefighter Kermit Easterling noted.

The department established an evacuation zone over a two-mile radius, and more than 5,000 residents were forced to leave the area; the precaution could remain in place for up to 48 hours, NBC News detailed.

Residents were staying at two shelters, including one at a local high school, explained David Kitchen, the senior disaster program manager for the American Red Cross's Tennessee volunteer region. Some of the affected individuals told the AP that they had not been aware of the train derailment until they were told of the evacuation order.

"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 recalled.