SOUTHFIELD, Mich. (AP) — Nearly half of about 300 Michigan fire departments said they have reserves of firefighting foam that has the potential to contaminate groundwater.

Michigan Fire Marshal Kevin Sehlmeyer told reporters Thursday in Southfield, Michigan, that approximately 32,000 gallons of the foam has been identified across the state from a survey of nearly 700 fire departments. About 400 departments have not yet completed the survey.

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The foam contains perfluoroalkyl and polyfluoroalkyl substances. Known as PFAS, the chemicals also have been used in waterproofing, carpeting and other products.

Sehlmeyer says the state is trying to find ways to dispose of the foam which primarily is used to suppress fires involving combustible liquids, like gasoline. Fire departments are being asked only to use the foam in emergencies and not during training.