TOKYO -- A U.S. fighter jet dumped two fuel tanks into a lake in northern Japan on Tuesday, creating a fuel slick, as about 10 fishermen were catching clams in boats below, officials said. No one was injured.

The U.S. Air Force said in a statement that an F-16 jet assigned to Misawa Air Base dumped the external fuel tanks after developing an engine fire while flying above Lake Ogawara.

The air force said the aircraft returned safely to the base, and there were no injuries to the pilot or people on the ground.

Japanese Defense Minister Itsunori Onodera said officials spotted parts believed to be from the aircraft in the lake. He said the water surface was smeared with fuel.

Japanese raise fists and shout slogans as they protest against the American military presence at Kadena Air Base in Cyatan, Okinawa, in this May 21, 2016 file photo. Getty

The local fisheries association and town officials were assessing the impact of the fuel leaking from the tanks. Clams, icefish and smelt are in season at the lake.

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Local fisherman Takao Ebina said his colleagues saw huge columns of water rising from the lake's surface about 100 yards from where they were catching clams.

"It's scary. They might have been hit if the fuel tanks had fallen a bit closer," he said.

There have been a series of recent incidents involving the U.S. military on the southern Japanese island of Okinawa, including parts of aircraft falling on schools.