(CNN) -- Hazardous materials teams are still cleaning up a toxic chemical spill from a  train derailment in Lafayette, Louisiana, on Saturday that forced 3,000 people from their homes.



Lafayette Police Sgt. Billy Soileau carries Ke'Iveion Solomon 2, as he helps evacuate children Saturday.



"Hazmat says that clean up is moving quickly and on track," Lafayette police said Sunday in a statement.



Two train cars leaked highly corrosive hydrochloric acid after the six-car train jumped the tracks Saturday about 2:30 a.m. CT (3:30 a.m. ET), according to police.



The chemical spill caused a toxic cloud to form above the site. Lafayette authorities evacuated about 3,500 homes and businesses -- including a nursing home -- within a mile of the derailment location.  Watch traffic detoured from cloud »



The Red Cross opened a shelter at Carencro High School for residents to stay Saturday night, while another 40 to 50 families were put up at hotel rooms, police said.



Residents will be allowed to return home once the spill is contained and no longer dangerous, said Joe Faust, a spokesman for BNSF Railway, which operates the train cars.



Hydrochloric acid is a clear, colorless solution of hydrogen chloride in water often used in metal cleaning and electroplating. Exposure to it can irritate the skin, said Lt. Craig Stansbury of the Lafayette Parish Sheriff's Office. People exposed to the substance are urged to seek medical attention.



Residents outside the evacuation area were advised to close windows and doors and turn off air conditioning to avoid any contamination.



Lafayette is about three hours west of New Orleans.
What happened from the chemical spill? What happened because of the derailment? WHat can irritate skin? What leaked acid? Is the chemical safe? What leaked from the train cars? What did authorities evacuate? Where did the cloud form? What does exposure to the chemical do?
caused a toxic cloud to form above the site. toxic chemical spill Hydrochloric acid Two train cars spill caused a toxic cloud to form above the site. highly corrosive hydrochloric acid about 3,500 homes and businesses above the site. irritate the skin,
question: What happened from the chemical spill?, answer: caused a toxic cloud to form above the site. | question: What happened because of the derailment?, answer: toxic chemical spill | question: WHat can irritate skin?, answer: Hydrochloric acid | question: What leaked acid?, answer: Two train cars | question: Is the chemical safe?, answer: spill caused a toxic cloud to form above the site. | question: What leaked from the train cars?, answer: highly corrosive hydrochloric acid | question: What did authorities evacuate?, answer: about 3,500 homes and businesses | question: Where did the cloud form?, answer: above the site. | question: What does exposure to the chemical do?, answer: irritate the skin,