State regulators said Friday natural gas along with crude oil contaminated west Bakersfield's drinking water this week when one or more valves were left partly open during preparations for a pressure test required by a recent emergency order against a local petroleum producer.

Griffin Resources LLC allowed gas pressurized at 150 pounds per square inch to backflow into the municipal water system, causing gas and oil to flow from faucets, toilets and sprinklers south of Lake Truxtun, according to California's Geologic Energy Management Division.