"Nobody really knows how dangerous it could be. However, it is in the system," Gov. Earl Ray Tomblin said Thursday night. "It's just so important, according to the health department, as well as West Virginia American [Water]: Please don't drink, don't wash with, don't do anything with the water."
The eight counties covered by the warning included Kanawha -- where the state capital Charleston is located -- Putnam, Boone, Jackson, Lincoln, Roane, Clay and Logan.
The Charleston Gazette reported the leak came from Freedom Industries.
State Environmental Protection Department spokesman Tom Aluise identified the chemical that leaked into the river as 4-methylcyclohexane methanol.
The warning by state officials triggered a rush for bottled water at grocery stores and convenience stores. The Gazette said while many restaurants were closed as a result of the water emergency, others remained open.
It wasn't clear when the warning would end, with Tomblin saying the state of emergency would stay in place until state health and environmental protection officials and the water company say the water is safe.
West Virginia American Water President Jeff McIntyre had told reporters earlier in the day the company was "fairly confident" its plant could handle the treatment of the chemical.
"It's clear the chemical has infiltrated the water," McIntyre said. "In an abundance of caution, we are taking these steps today."
McIntyre said the chemical is "not particularly lethal in its usage form" but its effects would depend on its concentration.
The Gazette said it had not been able to reach Freedom Industries officials, including company President Dennis Farrell, for comment.
The newspaper said Freedom Industries' website states it produces "freeze conditioning agents, dust control palliatives, flotation reagents [and] water treatment polymers," among other chemicals.
The chemical's toxicity was unclear, the newspaper said, with one material-safety data sheet stating while no specific information was available, "exposure to any chemical should be kept to a minimum."
"Skin and eye contact may result in irritation. May be harmful if inhaled or ingested," the document said.
The water company initially said the spill "does not present a health risk to customers."
"This is not a chemical that we deal with every day. It's not the type of thing we would see in dealing with a water treatment plant," McIntyre said. "We took some time to understand even what we were dealing with at the time."
McIntyre said the company would conduct "extensive flushing" to flush the contaminant out of its system.