By Karen Brooks

(Reuters) - West Virginia officials on Tuesday lifted a ban on drinking tap water from 35,000 customers who had been affected by a chemical spill that left the state's water supply nearly unusable for hundreds of thousands since last week.

Residents of the Southside and Southridge areas near state capital Charleston are now free to drink or wash with their tap water, according to a news release by West Virginia American Water. Downtown Charleston and nearby Kanawha City were cleared on Monday.

Consumers were instructed to flush their systems before using the water, which had been barred for use except for toilets since the chemical discharge into the Elk River on Thursday.

More than 300,000 consumers were affected after as much as 7,500 gallons (28,000 liters) of 4-methylcyclohexane methanol, or crude MCHM, leaked into the river.

"We're getting back to normal stage by stage," U.S. Senator Joe Manchin told MSNBC on Tuesday. "I would say by tomorrow everything should be back up and running."

Officials said on Monday that it might be several days before the entire system, with its hundreds of miles of pipe, is safe to use.

The crude MCHM chemical, which is used in coal processing, leaked into the river from a tank at a Freedom Industries site about a mile upriver from an American Water treatment plant, the biggest in the state.

Governor Earl Ray Tomblin declared a state of emergency in nine counties, including Charleston, shutting down schools and businesses.

Freedom Industries, which makes specialty chemicals for the cement, mining and steel industries, has apologized for the incident.

Water tainted by crude MCHM smells faintly of licorice. Contact with the water can cause nausea, vomiting, dizziness, diarrhea, rashes and reddened skin.

A total of 231 people had visited emergency rooms with symptoms, and 14 had been admitted, officials said.

The U.S. Chemical Safety Board and the U.S. attorney for the Southern District of West Virginia are investigating the spill.

West Virginia American Water is a unit of American Water Works Co Inc.

(Reporting by Karen Brooks; Additional reporting by Susan Heavey; Editing by Scott Malone and Lisa Von Ahn)