Construction vessels float on Oura Bay at the site of a future Marine Corps airfield for Camp Schwab, Okinawa, on Jan. 23, 2025. (Keishi Koja/Stars and Stripes)

A construction vessel spilled fuel oil at the site of a future Marine Corps airfield in northern Okinawa on Thursday, marking the third such incident this year, according to Japan’s coast guard.

The spill occurred at 4:05 p.m. while the vessel was pumping fuel oil from its tank to an onboard generator, the coast guard said in a news release that day. The oil overflowed from the generator’s tank and went into the ocean.

The vessel was working on the airfield project in waters about a half-mile north-northeast of Cape Henoko in Nago city. A contractor at the site reported the spill to the coast guard at 4:29 p.m.

Workers stopped the pump and deployed an oil fence and absorption mats to contain the spill. No oil was observed leaking beyond the fence by 5:34 p.m., according to the release.

An investigation is underway to determine the cause and amount of the spill, a coast guard spokesman said by phone Thursday. No injuries or environmental damage have been reported.

The incident follows two oil spills in January from vessels working on the airfield project. On Tuesday, another vessel towing construction materials for the site caught fire after oil leaked from its engine room.

The airfield is being built on reclaimed land in Oura Bay as a replacement for Marine Corps Air Station Futenma, which is situated in densely populated Ginowan city. The U.S. and Japanese governments agreed to the relocation in 1996, but legal challenges from the Okinawa prefectural government delayed construction.

The construction site is divided into two main sections: 279 acres on the northern side of Camp Schwab and 91 acres on the southern side, according to the Okinawa prefectural government’s website.