CHARLESTON, W.Va. -- It's been more than four days since a chemical seeped into a river and kept more than 300,000 West Virginians across nine counties from having clean tap water.
But as of Sunday evening, officials are confident the amount of the chemical in the local water supply is going down.
"I believe we're at a point where we can see light at the end of the tunnel," said Gov. Earl Ray Tomblin during a press conference at the state Capitol.
There are still tests and process that need to happen before residents have safe water, said West Virginia American Water Company President Jeff McIntyre.
"I can tell you at this point, I don't believe we're several days from starting to lift (the advisory), but I'm not saying today," McIntyre said.
As much as 7,500 gallons of the chemical, known as "crude MCHM," leaked through a hole in a storage tank at Freedom Industries early Thursday morning. An unknown portion of that leakage seeped through an old cement block wall meant to act as a secondary barrier and into the Elk River.
The leak happened roughly 1.5 miles from a treatment facility owned by West Virginia American Water. The company eventually had to tell 100,000 customers -- or roughly 300,000 people -- not to use the water for anything but flushing toilets and fire prevention.
The latest tests for the chemical near the water treatment facility are good, explained Adj. Gen. James Hoyer, head of the West Virginia National Guard.
A team of state officials determined a "flushing process" could start once water going into and coming out of the treatment plant contained less than 1 part per million of the chemical for 24 consecutive hours.
The U.S. Centers for Disease Control determined the 1 parts per million safe amount. Although little data is available about health effects of the chemical, local health and poison control officials say they are confident the measure is sufficient.
Hoyer said water passed the test Sunday. Results provided Sunday evening show since 9:02 a.m. Saturday, no water samples tested showed chemical levels higher than 0.92 parts per million.
The last two tests provided, taken at 6 a.m and 7 a.m. Sunday, didn't detect any amount of the chemical in water going into or out of the plant.
With these results, West Virginia American Water was able to start pumping clean water through the 1,700 miles of pipeline that runs through the affected system, McIntyre explained. Water that tested clean was running through the system for hours, as of the Sunday night press conference, he said.
The company will return useable water to different zones, he said. They'll focus on high-density, high-need areas first, where there are hospitals, nursing homes and more people.