BRUNSWICK, Maine (AP) — Maine environmental officials said all water samples analyzed so far in the wake of the state’s largest recorded accidental spill of firefighting foam are below its guidelines for potentially dangerous chemicals.

A fire suppression system at a hangar at Brunswick Executive Airport discharged more than 1,400 gallons (5,300 liters) of the foam concentrate mixed with 50,000 gallons (190,000 liters) of water at the former Navy base on Aug. 19. The discharge triggered an investigation and also prompted a warning from the Maine Center for Disease Control and Prevention to limit consumption of freshwater fish from nearby bodies of water.

The foam contained chemicals known as PFAS that are associated with health problems including cancer. The foam was removed after the accident.

The Maine Department of Environmental Protection sampled 34 water supplies in the area of the spill and has contacted property owners to discuss the results, the agency said Thursday. The water supplies will be tested every three months for a year, the agency said.

The department has also evaluated eight rounds of surface water results from the nearby watershed and found concentrations are continuing to decline, the agency said in a statement.

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“PFAS levels in the watershed have not yet returned to pre-spill concentrations and testing of surface water will continue to track the trends,” the department’s statement said.

Per-and polyfluoroalkyl substances, or PFAS, are found in everything from food packaging to clothing. The Environmental Protection Agency last year proposed limits on the chemicals in drinking water.

Some fire departments have also started to phase out using foam that contains PFAS because of concerns the chemicals leach into groundwater and can put firefighters at risk. PFAS are often described as forever chemicals because some don’t degrade naturally and are believed capable of lingering indefinitely in the environment.

The Maine Department of Environmental Protection said soil results have also been received from four areas identified as either most likely to be impacted by the foam release or having the greatest risk of potential exposure to recreational users. A preliminary review of the results shows some PFAS detected in all the soils tested, the department said. Comprehensive evaluation of the soil testing is still ongoing, the department said.

The department said fish and shellfish tissue samples will take longer to process. The advisories against consuming freshwater fish from nearby waterbodies remained on the Maine CDC website on Monday.

Maine CDC said it is advising residents to abstain from recreational activities such as swimming and boating that could result in contact with foam or affected waters until the effects of the foam release on bodies of water in the area have been thoroughly evaluated.