CLARENDON, Vt. (AP) — Additional testing of wells outside of a Vermont airport have found chemical contamination, but not enough for officials not to recommend the water for drinking.

The Rutland Herald reported Wednesday five wells in Clarendon had PFAS above state standard and 12 others have had some contamination, but not enough to pose a hazard to drinking water.

State officials believe firefighting foam used to extinguish a fire from a 1986 plane crash at the nearby Rutland-Southern Vermont Regional Airport may be the source of the contamination.

A “do not drink” order was issued earlier this year at a business park near the airport due to high levels of contaminants.

The order is expected to be lifted this month due to a new water treatment system.

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