COLORADO SPRINGS, Colo. (AP) — Drilling has begun on a test well near Peterson Air Force Base to determine how a foam used by military firefighters contributed to water contamination south of Colorado Springs.

The Gazette reports that drilling on the first of 18 wells began Thursday. The Air Force says the soil samples will be checked for perfluorinated compounds, or PFCs, contained in the firefighting foam.

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PFCs, which have been linked to prostate, kidney and testicular cancer, were found earlier this year in water systems serving about 69,000 people in Fountain, Security and Widefield.

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The chemical-laced firefighting foam was used at the base decades ago to fight fuel fires.

Another investigation into last week’s release of 150,000 gallons of water containing toxic chemicals at the base remains ongoing.

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