Hamada told reporters on Friday morning that they are still trying to ascertain what happened, and will take all possible measures to ensure safety in the operation of Self-Defense Forces aircraft.
The helicopter vanished Thursday afternoon
The Defense Ministry says a UH-60JA multi-purpose chopper vanished from radar while flying over waters north of the island of Miyakojima at around 3:56 p.m. on Thursday.
It says the helicopter was carrying 10 personnel, including the head of the GSDF's 8th Division, to which the craft belongs.
The ministry says the helicopter left a base on Miyakojima at 3:46 p.m. and was scheduled to return at 5:05 p.m.
It says wind velocity, visibility and other weather conditions near the island were good enough for a helicopter flight, and the crew members were checking their surroundings visually.
Coast guard officials say they have discovered what appear to be parts of the helicopter in waters near where it went missing. They have also found oil floating on the water surface.
The GSDF says a lifeboat found in the water belonged to the missing helicopter. The Defense Ministry is trying to confirm whether other parts are also from the helicopter.
A Coast Guard patrol vessel brought some of the parts back to a port on the island of Miyakojima on Friday afternoon, including a rotor blade and a door with the characters for the GSDF in Japanese. The blade was gouged near the bottom.
Yamazoe Takehiro of the Miyakojima Coast Guard Office is leading the search operation. He told reporters on Friday afternoon that they have deployed four patrol vessels but have found no signs of the missing people.
Local residents witnessed
Some people living in the area say they witnessed a helicopter in the air at roughly the time the aircraft went missing. A man from Ikemajima, an island adjacent to Miyakojima told NHK that he heard a loud noise and saw a helicopter equipped with what appeared to be a machine gun flying at a low altitude.
The Defense Ministry: likely an accident
The Defense Ministry says the incident was likely an accident, and has set up an accident investigation committee at the GSDF.
The GSDF has grounded all its helicopters of the same type, except for emergency dispatches.
A "stable performer"
A retired GSDF Lieutenant General has told NHK that the missing aircraft is a type that has proven to be stable for more than two decades.
Isobe Koichi, who served as a helicopter pilot, says the model has two engines to ensure stability of flight.
"The GSDF uses it for multiple purposes, including transferring personnel. The Maritime Self-Defense Force and Air Self-Defense Force also use the model for patrol or rescue operations," he says.
Isobe says there are various possible causes of the accident, including human error, mechanical problems, or collisions with an object such as a bird.
The Defense Ministry says the helicopter was carrying Lieutenant General Sakamoto Yuichi, who assumed the leadership of the 8th Division last week.
"It is important for a division head to understand the topography and conditions of islands," he says. "I assume Sakamoto may have wanted to check such things soon after taking office."