HUNTINGTON, W.Va. (AP) — A factory employee was treated for exposure to a toxic chemical Tuesday and about 200 people were ordered to stay indoors after a railroad car leak in southern West Virginia.

Huntington Fire Chief Tim Provaznik said the injured worker was taken to St. Mary's Hospital for observation after 50,000 to 60,000 pounds of aniline spilled while being unloaded at the Flint Group Pigments plant.

Aniline, used in manufacturing polyurethane, is toxic if inhaled, absorbed through the skin or swallowed.

Provaznik said the leak was contained inside the plant.

By early afternoon, employees from three nearby businesses that had been evacuated had returned to work and U.S. 60 had reopened to traffic, he said. The order to remain indoors was lifted nearly four hours after it was issued.

A crew from the state Department of Environmental Protection was supervising the cleanup, agency spokeswoman Kathy Cosco said.

The cause remains under investigation, though Provaznik said it might have been caused by an equipment malfunction.