TOKYO (AP) — Two Japanese Maritime Self Defense Force helicopters carrying eight crewmembers were believed to have crashed in the Pacific Ocean south of Tokyo during night-time training, Japan’s defense minister said.

The two SH-60K reconnaissance choppers, carrying four crew each, lost contact late Saturday near Torishima island in the Pacific about 600 kilometers (370 miles) south of Tokyo, Defense Minister Minoru Kihara told reporters.

One of the eight crewmembers was recovered from the waters, but his or her condition was unknown. The officials were still searching for the other seven.

The cause of the crash was not immediately known, Kihara said, adding that officials are prioritizing the rescue operation.

The MSDF deployed eight warships and five aircraft for the search and rescue of the missing crew, while they have recovered fragments believed to be of the SH-60K, Kihara said. “We believe the helicopters have crashed.”