CAMP FOSTER, Okinawa -- High levels of a banned pollutant have been detected in water running under Marine Corps Air Station Futenma, a year after the substance was found in streams and underground water wells adjacent to Kadena Air Base.

High concentrations of perfluorooctanesulfonic acid, or PFOS, and per-fluorooctanoic acid, or PFOA, were found during two underground-water surveys conducted in August and January, according to a statement released by the Okinawa prefectural government's environmental protection department.

PFOS and PFOA are virtually the same, Okinawan officials said, though their concentrations differ depending on the product.

PFOS and PFOA -- both synthetic, fully fluorinated organic acids -- are found in firefighting foam, aircraft grease, water-repellant materials and fluorine chemicals. They have been known to cause tumors, increases in body and organ weight and death in animals, Okinawan officials said. Their manufacture and importation have been prohibited in Japan since 2010.

Drinking water on and off base is safe despite the acids' presence in groundwater, said a spokesman from Ginowan City's water bureau. The water on and off base is supplied by the Chatan Water Treatment Plant, which also serves Kadena and the surrounding area.

"High levels of contamination was detected in underground water samples taken from the Oyama and Kiyuna districts," said Yoshinari Mi-yahira, team leader of the environmental protection department's water environments control team. "Both sit on lower grounds adjacent to Futenma."

Local officials said it isn't clear whether the material leaked recently or is from past contamination. When it was discovered outside Kadena last year, local officials in that case called for an immediate investigation, the suspension of its use and proper disposal of any on-hand stock.

Marine Corps officials did not respond to requests for comment.

In August, Okinawan officials found three locations out of 35 monitored throughout the prefecture that exceeded U.S. drinking water health advisory levels, which is 0.07 micrograms per liter, they said. All three -- 1.3, .21 and .71 micrograms per liter -- were adjacent and downstream from the air station.