About 500 homes, a school and several businesses were evacuated Thursday after a 22,000-gallon railroad tanker leaked chemicals into a creek and sewer system, prompting fears of a potential explosion.

An official with the Emergency Operations Center for Cabell and Wayne counties said the evacuation order probably would not be lifted until sometime Friday.

The tanker, leased by Marathon Ashland Petroleum (search), started leaking coal tar light oil Thursday morning, said company spokeswoman Linda Casey in Findlay, Ohio. The tanker was on a siding at the TechSol Chemical Co., and the leak occurred as workers were transferring the oil to trucks.

Jason Townson, one of the TechSol (search) employees, told WSAZ-TV it appeared a valve on the tanker was ruptured or broken.

No injuries were reported.

The oil is predominantly a mixture of benzene, toluene and xylene and is used in the production of petrochemicals at Marathon's Catlettsburg, Ky., refinery, Casey said. The company sent response teams to help with the cleanup.

Crews used a neutralizing agent in the cleanup and planned to flush the sewer system.

Because an explosion can result from a chemical buildup, Fire Chief Greg Fuller asked Wayne County school officials to send home about 500 students at a nearby elementary school. "He said he would feel better if we moved the kids out of the building," said schools Superintendent Gary Adkins.

About midday, officials decided to evacuate an entire two-mile radius — an area that included approximately 500 homes and a couple of businesses. The exact number of residents affected was not immediately available.

Several streets, including a section of U.S. 60, were temporarily closed.