Questions lingered about how and why the leak occurred and whether the company, Freedom Industries, took too long to let officials know about the problem that affected about 300,000 people and effectively shut down the state capital.
Tests over the weekend showed that levels of the chemical used in coal processing were consistently below a toxic threshold, but testing continued today.
"We see light at the end of the tunnel," Governor Earl Ray Tomblin told reporters. He announced today that the ban was lifted on parts of the region.
So far, 10 people exposed to the contaminated water were admitted to the hospital, and none was in serious condition, Health and Human Resources Secretary Karen Bowling said.
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About 28,400 liters of the chemical is believed to have leaked from a tank and containment area, and some of it got into the Elk River and the water treatment plant downstream.
The chemical quickly dissolves in water, so people have had to wait for it to pass through the water system or be diluted to the point where the water is again safe.
Freedom Industries' tanks don't fall under an inspection program, and the chemicals stored at the facility weren't considered hazardous enough to require environmental permitting.
Essentially, Freedom Industries wasn't under state oversight at all, said Michael Dorsey, chief of the state Department of Environmental Protection's Homeland Security and Emergency Response office.
"There's no question that they should have called earlier," Department of Environmental Protection Secretary Randy Huffman said.