Up to 300,000 people in West Virginia have been told not to drink tap water after the spill of a dangerous chemical sparked a federal emergency.

State governor Earl Ray Tomblin and President Barack Obama issued emergency declarations on Friday after the spill of up to 5,000 gallons of 4-Methylcyclohexane Methanol, or Crude MCHM, into the Elk River in Charleston. 

The release originated at Freedom Industries, a Charleston firm producing specialty chemicals for heavy industry.

Shops ran out of bottled water as residents rushed to buy supplies, forcing Tomblin to call for calm.

"If you are low on bottled water, do not panic. Help is on the way," Tomblin said. "We are taking every measure to provide water to you." He said supplies were moving into the area.

The governor said that there were several thousand gallons of the chemical at the Freedom Industries factory, and it is estimated that at the maximum about 5,000 gallons leaked out.

Gary Southern, the president of Freedom Industries, said that the company was still determining how much Crude MCHM had been released. 

"Our team has been working around the clock since the discovery to contain the leak to prevent further contamination," he said.  

Emergency workers distributed water to centres around the affected area. Residents formed long lines at stores and quickly depleted supplies of bottled water.

"It's just ridiculous," said Jaime Cook of Charleston.

"There's nowhere to buy water and everywhere seems to be sold out. This isn't going to last two days."

Source: Agencies