Japan asked the U.S. military Wednesday to ground F-16 fighter jets in the country after one jet dumped two fuel tanks in northeastern Japan before making an emergency landing the previous day, Defense Minister Nobuo Kishi said.

The Defense Ministry said it has made the request to suspend operations of F-16 fighters until their safety is confirmed, following the incident in Aomori Prefecture on Tuesday that triggered safety concerns as one tank apparently landed in a residential area although no one was injured.

Pieces of a fuel tank dumped from a U.S. F-16 fighter jet belonging to Misawa Air Base are pictured in the morning on Dec. 1, 2021, in Fukaura, Aomori Prefecture. (Kyodo)

Photo taken Dec. 1, 2021, from a Kyodo News plane shows the place (circled in red) where a fuel tank was found near a residential area in the Aomori Prefecture town of Fukaura, northeastern Japan, after being dumped by a U.S. F-16 fighter jet a day earlier. (Kyodo)

The ministry also called on the U.S. forces Tuesday to investigate the incident, officials said.

Kishi told reporters Wednesday he takes the matter "very seriously" and instructed ministry officials "to work closely with the United States to collect and analyze information to ensure that all possible measures are taken."

The 35th Fighter Wing of the Misawa Air Base said in a statement that an F-16 fighter jet experienced a problem during a flight and its pilot jettisoned the fuel tanks in an unpopulated area close to Mt. Iwaki in Aomori Prefecture.

The jet landed at Aomori Airport at around 6:10 p.m. on Tuesday. Police spotted bits of metal and liquid believed to be fuel about 20 to 30 meters from some homes in the town of Fukaura with a population of some 7,600, which is about 30 kilometers away from Mt. Iwaki.

The tank dumping follows a number of similar incidents by U.S. fighter jets in the northeastern prefecture in recent years.

Chief Cabinet Secretary Hirokazu Matsuno said in a press conference Wednesday the Japanese government has conveyed to the U.S. forces in Japan that the dumping was regrettable.

Col. Timothy Murphy, the vice commander of the 35th Fighter Wing of the Misawa Air Base, told Fukaura Mayor Mitsuru Yoshita as they met Wednesday, "We regret very much that the fuel tank came into the town. We are very thankful that it didn't injure anyone."

"What I can tell you, we have a very thorough investigation that we have started on the incident," he said.

Murphy also said it was regrettable the wing had initially said the pilot jettisoned the tanks in an unpopulated area.

Photo taken from a Kyodo News airplane shows a U.S. F-16 fighter jet belonging to Misawa Air Base at an airport in Aomori Prefecture on Dec. 1, 2021. (Kyodo)

Aomori Gov. Shingo Mimura told reporters Wednesday the prefectural government will make "a serious protest" to the U.S. military and the Defense Ministry over the matter.

Senior vice defense minister Makoto Oniki is visiting Aomori to bring local officials up to date on the incident.

Aomori Airport resumed operations on Wednesday morning after the emergency landing prompted the closure of the airport's lone runway, affecting several domestic flights, according to the prefectural government.

The Tohoku Defense Bureau said Wednesday it has confirmed that the metal objects found near the municipal government offices in Fukaura were from one of the two tanks dropped from the jet. The other tank has yet to be discovered.

"I heard a large sound and thought it was thunder. I was surprised that a U.S. jet had dropped it. I'm scared that it could have hit somebody," said a woman in her 80s.

In 2015, an F-16 fighter jet dumped its fuel tanks into the Sea of Japan off Aomori Prefecture, and another F-16 fighter ditched its fuel tanks into a lake near the Misawa base in 2018.

The Misawa base houses both the U.S. military and Japan's Self-Defense Forces.

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