A U.S. Air Force helicopter crashed Monday in a mountainous area within a base in Okinawa Prefecture, an accident that could further erode local sentiment toward the U.S. military presence.
Japan's Defense Ministry, informed by the U.S. forces of the crash, said three of the four crew members aboard the HH-60 rescue helicopter had been confirmed safe, but no other details were provided.
There were no reports of injury to local people, according to Okinawa prefectural police.
The U.S. Kadena Air Base in Okinawa said there were at least four people aboard and the Kadena-based helicopter was conducting a local training mission.
"We take safety in our operations very seriously," said a senior official of U.S. Forces Japan. "That is why we conduct extensive investigations to learn what happened so that we can make our operations as absolutely safe as possible."
The Japanese government described the accident as "regrettable" and asked the United States to conduct a thorough investigation and take preventive measures.
The United States promised to do so and to share its findings.
"This is an extremely important case," Defense Minister Itsunori Onodera told reporters.
Asked if the crash would have an impact on Japan's defense policy, Onodera declined to provide a clear answer, saying, "The crash just happened, so a thorough investigation is needed first."
Local police received an emergency phone call at around 4:45 p.m. reporting that smoke was rising from the U.S. Marine Corps' Camp Hansen.
Initial media reports on the crash triggered speculation that it may involve an Osprey tilt-rotor plane, the deployment of which has been opposed in Okinawa due to its poor safety record.
On Saturday, two Ospreys arrived at Okinawa's Futenma Air Station, part of a second batch to be deployed in Japan.
A series of dangerous accidents involving U.S. military aircraft have occurred in Okinawa.
A U.S. Air Force F-15 fighter crashed in waters off Okinawa in May and its pilot was rescued unhurt.
In August 2004, a U.S. Marine Corps helicopter crashed at Okinawa International University, leaving three crew members injured.