More than 100,000 customers were without safe tap water on Thursday after a chemical used to clean coal leaked into the Elk River in Charleston, W.Va., officials said.

West Virginia American Water warned residents in nine Charleston-area counties not to use the water. Gov. Earl Ray Tomblin declared a state of emergency, urging people not to drink, bathe, cook or wash clothes in the water.

The spill happened at a storage facility about a mile north of a water treatment plant on the Elk River, where a 48,000-gallon tank began leaking 4-Methylcyclohexane Methanol, or MCHM, a compound used to wash coal of impurities, the State Department of Environmental Protection said. The chemical spilled from a hole in the bottom of the tank and filled a container built to hold leaks before flowing into the river, Thomas J. Aluise, a spokesman for the agency, said.

Officials said they did not know how much of the chemical spilled into the river. Executives at Freedom Industries, the company that owns the storage tank, did not respond to emails seeking comment.