(CNN) -- More than 3,000 people were evacuated in Lafayette, Louisiana, on Saturday after two of six derailed train cars containing highly corrosive hydrochloric acid began leaking, authorities said Saturday.
The cars jumped the track about 2:30 a.m. CT.
About 3,500 homes, businesses and one nursing home were evacuated within a 1-mile area after toxic fumes rose from the site.
Residents will be allowed to return home once the spill is contained and no longer dangerous, which will take a day or two, said Joe Faust, a spokesman for BNSF Railway.
Lt. Craig Stansbury of the Lafayette Parish Sheriff's Office said it police officers were going door to door, ordering people to leave. A shelter was set up at Carencro High School.
Residents outside the evacuation area were advised to close windows and doors and turn off air conditioning to avoid any contamination. Watch what symptoms people should look for »
Lafayette is about three hours west of New Orleans.
Hydrochloric acid is a clear, colorless, solution of hydrogen chloride in water and is often used in metal cleaning and electroplating.
The acid can irritate the skin, Stansbury said, and people exposed to it were urged to seek medical attention.