TOKYO — A U.S. military helicopter crashed today at an American base on Okinawa, and all four crew members are believed to have survived, Japanese and U.S. officials said.

The HH-60 rescue helicopter, which belongs to Okinawa’s Kadena Air Base, was on an unspecified training mission when it crashed at Camp Hansen. TV footage showed smoke rising from a spot in the forest, with a mangled object that appeared to be a helicopter ablaze. The U.S. statement said the cause of the crash was not known. Defense Minister Itsunori Onodera told reporters that three crew members ejected and the fourth was apparently injured and taken to a hospital.