Letcher County residents have been warned not to use their tap water for anything but flushing toilets. Division of Water spokeswoman Allison Fleck says officials began investigating the contaminated water supply last weekend.“Around midnight on Sunday, the environmental response team pursued reports of a strong petroleum odor in the distribution system and traced that back to the water distribution in the plant," says Fleck.Fleck says officials have identified the source of the contamination, which was old, leaking petroleum storage tanks near the river that supplies the county’s drinking water. In November of last year, a similar leak led to prosecution of the owner of some old storage tanks. Fleck says legal action against the owner of the leaking tanks this time around is pending but not yet public.