Thousands of people remained evacuated from their homes Sunday as hazardous material workers cleaned up hydrochloric acid that spilled when six train cars derailed a day earlier.

Saturday’s derailment spread a toxic cloud over the city. Five people, including two railroad workers, were sent to a hospital and treated after complaining of skin and eye irritation, State Police Trooper David Anderson said.

Anderson said he couldn’t estimate how long the cleanup and evacuation would take. Hazardous materials specialists have to work cautiously because the acid is so dangerous.

Hydrochloric acid can cause respiratory problems and skin and eye irritation, said Joe Faust, a spokesman for Texas-based BNSF Railway, which operated the train.

An estimated 8,000 to 10,000 gallons spilled, forming a yellowish pool.

All six rail cars were restored to an upright position, and some had been moved out of the 1-acre contamination site, Anderson said. “The stuff we’re dealing with is bad _ very bad stuff,” he said.

A nursing home with 161 residents was evacuated, and about 35 of the residents were taken to area hospitals because they were too frail to be moved to other facilities, state officials said.

The Red Cross set up a shelter at a high school but no one was using it on Sunday, Anderson said. Most of those evacuated were with family and friends, and some were put up in hotels by the rail company, he said.

Lafayette is about 125 miles west of New Orleans.