The Suffolk County Department of Health Services is seeking to test private wells on more than 90 properties near the East Hampton Airport in Wainscott after elevated levels of chemicals were detected in a nearby private water supply, officials said Wednesday.

Of 25 private wells tested within a square mile of the airport since late August, one had perfluorinated compounds above the federal health advisory level of 0.07 parts per billion, health officials said.

Exposure to the chemicals can affect the immune system and fetal health and development, as well as cause liver damage, cancer and thyroid problems, the Environmental Protection Agency has said.

Town officials said they are providing free bottled water to area residents as a precaution.

Health officials said they began testing wells after the state Department of Environmental Conservation conducted a survey in which the East Hampton Airport indicated it had used or stored products that may have contained perfluorooctanoic acid and/or perfluorooctanesulfonic acid, known respectively as PFOA and PFOS.

Airport manager Jim Brundige said no chemicals with PFOS or PFOA are stored there.

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Town Supervisor Larry Cantwell said the contamination may have come from firefighting foam and that all fire departments within East Hampton will be contacted to determine when and where the foam may have been used.

“We’re going to work closely with the health department and cooperate so the full extent of the problem can be determined, and then we’ll work on a permanent solution,” Cantwell said.

The same perfluorinated compounds have contaminated wells in Hampton Bays, near a Hampton Bays Fire District parcel, and in Westhampton Beach, near Francis S. Gabreski Air National Guard Base.

The level of perfluorinated chemicals in Wainscott’s public drinking water supply is below the federal health advisory, health officials said.

Health officials are seeking to test properties within about a square mile south of the airport.

Residents can call 631-852-5810 to have their wells tested for free, and 631-324-4183 to get free bottled water.