A freight train carrying a highly flammable and toxic substance partly derailed and caught fire around midnight on Thursday near Knoxville, Tennessee, officials said.
The CSX train, which was traveling from Cincinnati, Ohio, to Waycross, Georgia, was carrying acrylonitrile, a substance used in the manufacture of acrylic acid and modacrylic fibers. Exposure in high levels, particularly when inhaled, can cause anemia, headaches, jaundice, kidney problems and nausea.
At least seven first responders were taken to the hospital after breathing in the fumes from the blaze, Blount County Sheriff's Department spokeswoman Marian O'Briant told NBC News.
The derailment has prompted officials to issue mandatory evacuation orders within a one-mile radius of the derailment, Blount County Sheriff's Office stated on Facebook.
At least 5,000 residents are urged to take shelter at the Foothills Mall and Heritage High School in Maryville, local NBC affiliate WBIR reported. They may have to remain there for 24 to 48 hours.
At the time of this writing, the cause of the derailment is not known.