A chemical spill left the water for 300,000 people in and around Charleston, West Virginia, stained blue-green and smelling like licorice. Officials said it was unclear when it might be safe again even to take showers and do laundry.
The spill brought the state's capital and most populous city to a virtual standstill, closing schools and offices and forcing the legislature to cancel its business for the day.
Officials focused on getting water to people who most needed it, particularly the elderly and disabled.
As they moved to bring water to the affected people, the US attorney for the Southern District of West Virginia opened an investigation into how as much as 19,000 litres of a chemical used to process coal leaked into a river on Thursday and found its way into Charleston's water-treatment plant.
West Virginia Governor Earl Ray Tomblin and US President Barack Obama declared emergencies on Friday.
Tomblin ordered people in affected areas to "continue to refrain from using the water for drinking, cooking, cleaning, bathing and washing".
Obama directed the Federal Emergency Management Agency to assist the state and provide federal funding for the effort.
"Downtown Charleston is dead," Mayor Danny Jones said. "It's not just my city, it's nine counties. When you don't have water you can drink or bathe in, you're pretty much frozen solid."
Jones said hotels, restaurants and affiliated businesses were closed in the city of 51,000 people, which swells to about 125,000 on an average working day.
The chemical, 4-methylcyclohexane methanol, a solvent used in processing coal, leaked from a tank at Freedom Industries and escaped a containment area.
Bill Price, who lives in Charleston about 2.5 kilometres from the confluence of the Elk and Kanawha rivers, said the odour on Thursday led residents to believe that there had been a release of chemicals into the air, before word began to spread about the spill into the river.
"We're being told that this is not a toxic chemical," he said. "But then at the same time, we're not allowed to bathe in it."
Price said he was drinking orange juice on Friday and planned to go out later to see whether water was available.
Officials and experts say the chemical, even in its most concentrated form, is not deadly. However, people across nine counties were told they should not even wash their clothes in affected water, as the compound can cause symptoms ranging from skin irritation and rashes to vomiting and diarrhoea.
By Friday evening, 737 people had called the West Virginia Poison Centre to report concerns or symptoms related to the spill, said director Elizabeth Scharman. Those with symptoms reported nausea, vomiting, dizziness, diarrhoea, rashes and/or reddened skin, she said.
Few people had been brought into emergency rooms with symptoms that might have stemmed from the chemical, and none was in serious or critical condition on Friday, said state Health and Human Resources Secretary Karen Bowling.
The company where the leak occurred, Freedom Industries, discovered on Thursday morning that the chemical was leaking from the bottom of a storage tank, said its president, Gary Southern.
He said the company worked all day and through the night to remove the chemical from the site and take it elsewhere.
Vacuum trucks were used to remove the chemical from the ground at the site.
Associated Press, Reuters, The Washington Post