Federal prosecutors are opening an investigation into a chemical spill that’s contaminated the water supply for more than 200,000 people in West Virginia, according to a statement released by the U.S. Attorney's Office for the Southern Distrct of West Virginia.

“Yesterday’s release of a potentially dangerous chemical into our water supply has put hundreds of thousands of West Virginians at risk, severely disrupted our region’s economy, and upended people’s daily lives,” U.S. Attorney Booth Goodwin said in a statement. “My office and other federal law enforcement authorities have opened an investigation into the circumstances surrounding the release. We will determine what caused it and take whatever action is appropriate based on the evidence we uncover.”

The chemical spill in question occurred on Thursday at a storage facility on the Elk River “where a 48,000-gallon tank began leaking 4-Methylcyclohexane Methanol, or MCHM, a compound used to wash coal of impurities,” into another container, which overflowed into the river, according to The New York Times.

West Virginia Governor Earl Ray Tomblin has declared a “State of Emergency” in the affected counties of Boone, Cabell, Clay, Jackson, Kanawha, Lincoln, Logan, Putnam, and Roane, and has dispatched the state’s Department of Environmental Protection to Freedom Industries to halt further leaching of MCHM into the river.

“West Virginians in the affected service areas are urged not to use tap water for drinking, cooking, washing, or bathing,” Tomblin said in a statement, as the chemical can cause headaches, eye and skin irritation, and difficulty breathing if exposed for long periods of time in high concentrations.

Tomblin requested a federal emergency declaration to assist with the affected areas, which the White House approved just past midnight this morning. In addition, Tomblin has been working with the National Guard and West Virginia’s Office of Emergency Services to distribute water supplies to the affected counties, focusing on nursing homes and schools, many of which have been cancelled for the day because of the lack of tap water. At this time officials do not know how much MCHM has been leaked into the river, or what its potential health implications may be, according to The Times.