Five thousand residents have been evacuated from a one-mile radius around a derailed train carrying toxic gas, which has caught fire near Maryville, Tennessee.
Seven firefighters have been taken to hospital after breathing fumes from the blaze, according to Blount County Fire Department.
In a statement the county's sheriff's office said at least one of the freight train's cars was carrying "highly flammable and toxic gas".
It added that the evacuation could last from 24 for 48 hours and that a Red Cross shelter had been set up at a local high school.
NBC news reported that as many as three carriages had caught fire, adding that the train was carrying Acrylonitrile, a gas used in the manufacturing process for certain plastics.