Four people have been hospitalised and several hundred thousand remain without water after a chemical leaked from a storage tank in West Virginia's capital city into the public water treatment system, state authorities said Saturday.

On Saturday, about 300,000 people in nine counties entered their third day without being able to drink, bathe in, or wash dishes or clothes with their tap water, after a foaming agent escaped the Freedom Industries plant in Charleston and seeped into the Elk River. The only allowed use of the water was for flushing toilets.

Allison Adler of the Department of Health and Human Resources said 32 people sought treatment at area hospitals for symptoms like nausea and vomiting. Of those, four people were admitted to the Charleston Area Medical Center. Their conditions were not immediately known. Adler added that authorities were still trying to figure out the safety level of the water and that more information should be available to residents later on Saturday.

In the first hours after the spill, residents concerned about potential health effects deluged the West Virginia Poison Center with calls. Adler said about 50 people called with queries about keeping goats, chicken and other farm animals safe from exposure. Federal authorities, including the Occupational Safety and Health Administration, or OSHA, opened an investigation into Wednesday's spill. Just how much of the chemical leaked into the river was not yet known.

The company's president issued an apology to West Virginia residents.

"We'd like to start by sincerely apologizing to the people in the affected counties of West Virginia," Gary Southern said. "Our friends and our neighbors, this incident is extremely unfortunate, unanticipated and we are very, very sorry for the disruptions to everybody's daily life this incident has caused."

Some residents, including John Bonham of Cross Lanes, were willing to accept the apology.

"Yeah, I understand that stuff can happen," said Bonham, who also works in the chemical industry. "I don't think it's going to get him out of legal liability. OSHA is the one they're going to have to answer to."

The leak was discovered on Thursday morning. Southern 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.

"We have mitigated the risk, we believe, in terms of further material leaving this facility," Southern said. He said the company didn't know how much had leaked.

The tank that leaked holds at least 40,000 gallons (151,000 litres), said a state Department of Environmental Protection spokesman, Tom Aluise, although officials believe no more than 5,000 gallons (18,900 litres) leaked from the tank. Some of that was contained before escaping into the river, Aluise said.

Freedom Industries was ordered Friday night to remove chemicals from its remaining above-ground tanks, Aluise added.

The company was already cited for causing air pollution stemming from the odor first reported Thursday, Aluise said.

The primary component in the foaming agent that leaked is the chemical 4-methylcyclohexane methanol. The spill has forced businesses, restaurants and schools to shut down and forced the state Legislature to cancel its business for the day.

Governor Earl Ray Tomblin said the Federal Emergency Management Agency and several companies were sending bottled water and other supplies for residents. "If you are low on bottled water, don't panic because help is on the way," Tomblin said.