Lafayette, La. - Six cars of a freight train derailed early Saturday, including one that began leaking hydrochloric acid, causing thousands of people to evacuate homes, businesses and two nursing homes within one mile of the wreck.

The spilled acid sent a toxic cloud over the area, and at least five people, including two railroad workers, were taken to a hospital and treated after complaining of skin and eye irritation, said Lafayette Parish sheriff's Lt. Craig Stansbury.

Acadian Ambulance official Clay Henry said 20 bed-bound residents of the Our Lady of the Oaks nursing home taken to a hospital.

Police walked door-to-door notifying residents of the mandatory evacuation in an area with an estimated population of 3,500 people. "We're advising them to take enough supplies for approximately 48 hours," Stansbury said.

Mona Hebert and Jeffrey Ferrara said they were rousted from their trailer around 3:45 a.m. and told they had two minutes to leave. Ferrara, who lost his home in Hurricane Katrina and has been staying with friends like Hebert since then, didn't have time to grab his shoes or any of his medications.

"This is gravy compared to" Katrina, Ferrara said, adding that the morning air smelled of chlorine, like a swimming pool.

Hydrochloric acid can cause respiratory problems and skin and eye irritation, according to Joe Faust, a spokesman for the Texas-based BNSF Railway that operated the train involved in the spill.

Faust said BNSF was sending lime to the area to neutralize the hydrochloric acid. He declined to speculate on how long the cleanup might take but said residents wouldn't be allowed back into the area until officials were certain the hazardous material was gone.

"We want to make sure that they're not returning home prematurely," Faust said. "We want to make sure the entire area is clean."

The Red Cross has set up a shelter at a high school and was gearing up to handle as many as 500 people if possible, shelter manager Jacqui Picard said. By late Saturday morning, the shelter was offering snacks, drinks and a cool place to stay. One person was seen napping on the bleachers; volunteers were milling around.

___Associated Press writer Michael Kunzelman contributed to this report.