The commanding officer of the Japan Maritime Self-Defense Force says an accident investigation committee will be set up to determine the cause of Saturday's fatal crash of two of its helicopters. He also pledged to accelerate search efforts for the missing.

The MSDF chief of staff, Admiral Sakai Ryo, held a news conference on Sunday.

Two SH-60K patrol helicopters, each with a crew of four, crashed off the Izu Islands in the Pacific Ocean. The accident left one person dead and the others missing.

Sakai said a pilot, a co-pilot and two navigators were on board each aircraft. He also said the pilots were identified as Lieutenant Commander Matsuda Takuya stationed at an air base in Nagasaki Prefecture, and Lieutenant Commander Itamura Kazuki from an air base in Tokushima Prefecture.

Three helicopters were engaged in a submarine location drill.

Sakai said two flight recorders recovered at the crash site had been sent to a unit tasked with analyzing data.

The Defense Ministry says the two recorders were found close to each other, suggesting that the helicopters probably collided in mid-air.

The admiral said it is regrettable such a tragedy occurred, and apologized for the concern caused by the accident. He also said that based on lessons learned from past accidents, he had instructed MSDF personnel to carefully check altitude and distance during flight training.