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The latest tests of poisoned water in West Virginia have shown that the quality is improving "in the right direction," the state's governor said Sunday.

It's a hopeful sign for the 300,000 residents currently under a strict tap water ban following a chemical spill four days ago.

"We are at a point where we can see a light at the end of the tunnel," Governor Earl Ray Tomblin said at a news conference.

But officials stopped short of saying when the do-not-use order would be lifted.

Read the full story on NBC News' website.