A fire at a hazardous waste incineration plant forced hundreds of residents to evacuate Sunday, officials said.

No injuries were reported and officials were monitoring air quality as thick smoke rose from the Teris plant in southern Arkansas (search), said Union County Sheriff Ken Jones.

Police estimated about 1,500 people within a few miles of the plant were evacuated, including some in this city of about 23,000.

After U.S. Environmental Protection Agency (search) officials tested air and soil in the area, many of those evacuated were allowed to return to their homes Sunday night. But about 500 people had to spend the night elsewhere, El Dorado police Chief David Smith said.

Doug Riley, vice president of operations for El Dorado-based Teris LLC (search), said a worker discovered the fire about 8 a.m.

Residents reported hearing a series of explosions and one person said it rattled the windows of his home.

Riley said the fire was out by Sunday afternoon, "except for one small area in the storage building." The company and fire and police departments agreed to let the fire burn out rather than send firefighters into the hazardous area, he said.

Riley said the waste chemicals included substances sent by customers from throughout the country for disposal, including mixed solvents, cylinders of different types of gases and a variety of batteries.

Chris Ruhl, the EPA's on-scene coordinator, said the air quality was fine for people outside evacuation zones. He wouldn't comment on the air inside the zones, saying the EPA was continuing to monitor air quality along with state officials, and was making sure their readings were consistent with the company's.

Ruhl added that because of what the fire was burning, the materials being released into the air could be changing frequently.

Sunday church services were canceled because of the fire, and authorities were advising people not to use their air conditioners and to keep their doors shut as a precaution.

Shelters were set up at churches and community centers for people displaced from their homes, including residents of nursing homes who did not need to be transferred to hospitals.

Herman Hill and his wife planned to stay at a church shelter. He said his asthma had been bothering him since the thick cloud of smoke began covering the city.

"We need some face masks," said Hill, 49. "We didn't seal off our house or our air conditioner. Will the chemicals get into our food? I'm worried."

About 150 inmates from the county jail were evacuated to a school gymnasium before being moved to other jails Sunday night, Smith said.

Teris disposes of hazardous waste from industries and government operations, including spent solvents, waste oils, chlorinated hydrocarbons, herbicides and insecticides, as well as dirt, residues and contaminated water from cleanup activities from other sites.