A U.S. military HH60 Pave Hawk helicopter carrying four personnel crashed during a training exercise on Japan's southern island of Okinawa on Monday, officials said.
There was no immediate word on the status of those on board, according to a statement from U.S. Air Force spokeswoman 1st Lt. Hope Cronin.
U.S. military firefighters were tackling a blaze resulting from the crash, she said.
The crash took place at 4 p.m. local time Monday (3 a.m. ET Sunday) at a maneuvering ground inside the U.S. Marine's Camp Hansen in central Okinawa.
"This is really regrettable. We are asking the U.S. side for a speedy supply of information," Japan's Defense Minister Itsunori Onodera told reporters, according to Reuters. "We plan to strongly demand for investigation into the cause of the accident and measures to prevent a recurrence."