Pico Rivera, Calif. ? A freight train carrying hazardous materials derailed early Saturday, damaging at least four homes and forcing more than 200 people to evacuate, officials said. No serious injuries were reported.

Investigators were trying to identify the hazardous materials on board and determine whether any leaked when the nearly 50 freight cars and trailers left the tracks, Los Angeles County Sheriff’s Deputy Luis Castro said. About 500 gallons of diesel fuel spilled.

Derailed cars badly battered two homes and littered several back yards with twisted metal and debris. One boxcar went through the roof of a home, and two others smashed into a wall outside a house next door.

One resident was treated at the scene for injuries caused by debris, Castro said.

Union Pacific spokesman John Bromley said the train carried “things like paint and batteries,” but Los Angeles County fire inspector John Mancha said there also were small quantities of sulfuric acid, a resin solution and butane lighters.

The train had been en route from Los Angeles to Marion, Ark., when it derailed in the Los Angeles suburb of Pico Rivera.

Sara Fabela, 33, was home when she heard the train approaching. She said she thought the ground was shaking more than it usually does when trains pass, then she heard a loud crash and the lights went out.

“I opened the door and there was thick black smoke everywhere. The smoke had a funny smell,” she said.

Fabela, who is five months pregnant, said she developed a headache soon after the accident and was concerned about the health of her fetus.

“They say it was small amounts (of hazardous materials), but you never know,” she said.

The accident was Union Pacific’s second in as many years in the Los Angeles area.

In June 2003, 13 people were injured and several homes were damaged or destroyed when a Union Pacific train jumped the tracks in Commerce, Calif., about 10 miles from Pico Rivera. Local leaders criticized the railroad’s emergency procedures following the incident.