TOKYO (AP) — Two Japanese Navy helicopters carrying a crew of eight crashed into the Pacific Ocean south of Tokyo during a night training exercise in a possible collision, killing one person as rescuers searched Sunday for seven others missing, according to a report. The Minister of Defense said.

The two Marine Self-Defense Force SH-60K helicopters were carrying a crew of four and lost contact late Saturday near Torishima Island, about 600 kilometers south of Tokyo, Defense Minister Minoru Kihara told reporters.

Kihara said the cause of the accident was not immediately known, but officials believe the two helicopters “very likely” collided before falling into the water.

Chief of Naval Staff Admiral Ryo Sakai said training on the SH-60 aircraft would be suspended until the cause of the crash was determined and preventive measures were taken.

Rescuers recovered a flight data recorder, a blade from each helicopter and fragments believed to be from the two helicopters in the same area, signs that the two SH-60K helicopters were flying close to each other, Kihara said.

Search and rescue efforts for the missing crew were expanded on Sunday with the deployment of 12 warships and seven aircraft. Japanese Coast Guard boats and aircraft also joined the operation.

US Ambassador to Japan Rahm Emanuel offered his country's assistance in search and rescue operations.

He added: “We will stand side by side with our friend and ally, Japan. “My thoughts are with the crew members, their families and friends during this difficult time,” he wrote on social media platform X.

The twin-engine, multi-role helicopters developed by Sikorsky and known as Seahawks were modified and produced in Japan by Mitsubishi Heavy Industries. Kihara said they were receiving night anti-submarine training. Someone lost contact at 10:38 p.m. and sent out an automatic emergency signal a minute later.

Kihara said only one distress signal was heard, called an emergency locator transmitter, which is another sign that the helicopters were close to the same place, because their signals use the same frequency and are indistinguishable.

One of the helicopters belongs to an air base in Nagasaki, and the other to a base in Tokushima Prefecture. Kihara said officials were interviewing the pilot of a third plane that also participated in the training on Saturday.

The SH-60Ks are usually deployed on destroyers for anti-submarine warfare, but are also used for search and rescue operations and other missions. Japan owns about 70 modified helicopters.

Defense officials said Saturday's exercises only involved the Japanese Navy and were not part of a multinational exercise.

Japan under Security Strategy 2022 It has accelerated its military buildup and strengthened deterrence on the islands southwest of Japan in the Pacific Ocean and the East China Sea to counter threats posed by China's increasingly aggressive military activities. In recent years, Japan has conducted extensive naval exercises in addition to joint exercises with its ally, the United States, and other partners.

The Japanese Navy Chief of Staff said that the training that took place on Saturday was part of routine exercises in which warships, submarines and Seahawk helicopters participated. During training, a number of helicopters hover together while lowering sonar into the water to detect submarines.

In 2017, a Japanese Navy SH-60J, a previous generation Seahawk, crashed during a night training exercise due to human error, killing three crew members. In July 2021, two SH-60 aircraft were involved in a minor collision off the southern island of Amamioshima, both sustaining blade damage, but no casualties.

Following the 2021 collision, the Navy introduced a range of precautions to ensure adequate distance between aircraft. Sakai said Saturday's accident could have been prevented if all safety measures had been properly followed.

In the United States, the fatal crash of an MH-60S Seahawk during training off California in 2021 was attributed to mechanical failure due to unexpected damage during maintenance, according to the Navy.

The incident in Japan also comes a year after the Ground Self-Defense Forces were deployed UH-60 Black Hawk crashed off the southwestern island of Miyako due to an engine output problem known as “rollback”, killing all ten crew members.

Japanese public broadcaster NHK said no weather warnings had been issued for the area at the time of the accident on Saturday.