BRUNSWICK, Maine (AP) — Firefighting foam in a hangar at Brunswick Executive Airport has been been removed, and mitigation is underway on four retention ponds following Maine’s biggest accidental spill of the fire suppressant on record, officials said Monday.

The Maine Center for Disease Control and Prevention advised the public not to consume or to limit consumption of freshwater fish from four nearby bodies of water following the accidental discharge of firefighting foam containing harmful chemicals known as PFAS.

An investigation is underway into why a fire suppression system discharged Aug. 19 in Hangar 4, releasing 1,450 gallons (5,490 liters) of firefighting foam concentrate mixed with 50,000 gallons (190,000 liters) of water at the former Navy base. Federal records show the spill is the biggest accidental discharge in Maine since its recordkeeping began in the 1990s.

Aircraft that were doused are undergoing a final cleaning inside the hangar, and then the hangar will be cleaned for a final time, officials said Monday. Four vacuum trucks were deployed to remove foam from the retention ponds, officials said.

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PFAS are associated with health problems including several types of cancer, and they are found in everything from food packaging to clothing, in addition to firefighting foam. Last year, the Environmental Protection Agency, for the first time, proposed limits on the so-called forever chemicals in drinking water.

The Maine Department of Environmental Protection is overseeing the remediation at the former Brunswick Naval Air Station, now known as Brunswick Landing. The base, which officially closed in 2011, had automated fire suppression in large hangars that once housed P-3 Orion patrol aircraft and other planes.