text: The train was carrying a flammable, toxic substance called acrylonitrile when it came off the rails near Maryville, just outside Knoxville.
  Firefighters evacuated people within a two-mile radius of the fire to prevent them breathing in the poisonous fumes.
  Local police said seven officers were hospitalised because of the fumes.
  The train was pulling 57 carriages of mixed freight from Ohio to Georgia when it derailed just before midnight on Wednesday, the train's operators CSX said in a statement.
  One of the carriages transporting acrylonitrile burst into flames.
  Acrylonitrile is a chemical compound used to manufacture plastics. Officials say it is "highly flammable and toxic" and can cause headaches, nausea and kidney irritation if inhaled.
  Firefighters wearing breathing equipment went door-to-door telling Maryville residents to move to temporary shelters, one of which has been set up in a high school out of the at-risk area.
  Locals have been told the evacuation could last up to 48 hours.
target: More than 5,000 residents of the US state of Tennessee have been evacuated after a freight train carrying toxic chemicals derailed and caught fire.