TOKYO -- Japanese authorities have conducted an on-site inspection of the US Yokota Air Base in western Tokyo over the possibility that water contaminated with per- and polyfluoroalkyl substances (PFAS) overflowed from the base, local media reported Friday.

The inspection came two months after the US military informed the Japanese side that the water containing PFAS synthetic chemicals had leaked from an area of the base where a firefighting drill was being carried out.

Officials from the defense ministry, the foreign ministry, the environment ministry, Tokyo's metropolitan government as well as local municipalities entered the base on Friday morning, Kyodo News reported.

They inspected the firefighting training area where the leakage was believed to have occurred and water samples from the reservoir in the firefighting training area were expected to be taken in the future, the report said.

"This inspection was conducted in response to the fears and concerns harbored by local residents, and we will continue to work together with the US side," Fumitoshi Sato, deputy chief cabinet secretary, told reporters.

PFAS, used in a wide variety of products including fire extinguishers, is known as "forever chemicals" because it breaks down very slowly over time and can accumulate in people, animals, plants and the environment.

The US military in Japan has already stopped using extinguishers that include PFAS, but past US investigations had detected in reservoirs levels far above Japan's nonbinding interim standards.

Japan's food safety panel previously concluded that the effects of PFAS on birthweight loss and reduced immunity are "undeniable," even though "evidence is limited" regarding the potential of PFAS to cause cancer.

On Oct 3, Tokyo officials received a report from the US military through the defense ministry that approximately 48,000 liters of PFAS-contaminated water overflowed from the firefighting training area at the base during heavy rainfall on Aug 30.