VALLEY CENTER, Kan. – A day after an explosion and fire at a solvents plant, emergency crews struggled to find enough tankers and other equipment to clean up hundreds of thousands of gallons of chemicals that continued to spew toxic vapors into the air.

Most residents of this community of 6,000 just north of Wichita who had left because of the fire were allowed to return to their homes Wednesday morning, more than 24 hours later. Investigators said Wednesday the blaze was started by static electricity as workers filled a tank that had a dry-cleaning product in it.

The area closest to the Barton Solvents plant in downtown Valley Center remained off-limits Wednesday, with city officials sternly warning those residents, some of whom had tried to sneak back into their homes, that the air remained a health risk there.

George Malvaney, vice president of emergency operations for United States Environmental Services, which was hired by Barton Solvents to handle the cleanup, said his firm was trying to get enough trucks and storage tanks to remove about 300,000 gallons of liquids that remain. Malvaney said his company was bringing tankers in from other parts of Kansas, as well as from Oklahoma, Texas and Mississippi.

On Wednesday, workers scraped the surface soil to a depth of six inches to a foot in the most heavily contaminated areas and expected to remove 300 to 350 cubic yards of contaminated material.

Homeowner Ron Black and his wife were so anxious to get back into their home after spending the night at a Newton motel that they walked past barricaded roads with their luggage in tow.

“We are going to walk in to check on our cats. That’s the stupidest thing I’ve heard of, but it’s the truth,” said Black, whose home was in a section of town officials had just reopened.

His wife, Linda, said the couple debated whether to take their animals with them when they evacuated but did not have good enough cages.

“She lost so much sleep over these cats,” said Susan Douglas, her sister who was visiting from California when the family was evacuated.

Meanwhile, some disappointed residents returned to find their neighborhoods still blocked.

Ray Woods and his wife, Lynda, were turned away by police at several entrances to their neighborhood less than a mile from the plant. They had spent the night at a Park City motel, but he had left medications and a tank of oxygen at their house.

“I am still alive. I made it all right without it,” Ray Woods said. “The real reason I want to get back in to get my medication.”

David Higday, an investigator for the Kansas State Fire Marshal’s Office, said the fire was caused by a static charge that ignited vapors from a dry-cleaning product. He said the blaze began even though workers were using proper procedures and the tank they were filling was grounded.

The first blast happened around 9:15 a.m. Tuesday, causing a blaze that sent black smoke billowing from storage tanks and igniting about 660,000 pounds of chemicals, officials said. Flames shot as high as 200 feet into the air, and 15 or more secondary explosions could be heard. At one point, 36 of the plant’s storage tanks were on fire, officials said.

The burning storage tanks contained industrial chemicals, including hydrocarbons, alcohol and ketones, used in the paint and coatings industry.

Initially, firefighters concentrated on defending nearby buildings, and some residents were ordered to evacuate. Officials urged others to leave as well.

Those who didn’t evacuate were told to stay inside with the windows closed and air conditioners off, even as temperatures topped 90 degrees.

Twelve people went to a Wichita hospital as a precaution, said Helen Thomas, a spokeswoman for Wesley Medical Center. All of them were examined and released Tuesday, she said.

David Casten, president of Des Moines, Iowa-based Barton Solvents, said that the plant employs about two dozen people and that about 12 were working Tuesday morning. All employees were safe, he said.

The state had planned to send Kansas National Guard troops to help with security and public safety, but the adjutant general’s office said Wednesday that they were no longer needed because the fire had been extinguished.