Japan's defense minister says U.S. chopper crash "regrettable" TOKYO, Aug. 5 (Xinhua) -- Japanese Defense Minister Itsunori Onodera said Monday that the crash of a U.S. military helicopter in Okinawa prefecture was "regrettable," calling for a thorough probe into the accident. "As any crash of aircraft could be a dangerous accident, proper preventive measures are important," Onodera was quoted by local media as saying. Three of a total of four crew members in the crashed helicopter have been confirmed safe, one of them has been taken to hospital, according to the minister. It is unclear whether the other two escaped crew members were injured. One crew member remains missing. The HH-60 helicopter crashed down at about 4:30 p.m. local time, when it was in a training mission near Ginoza village in the northern area of the prefecture, according to the U.S. Kadena base that also located in Okinawa. The Japanese Defense Ministry has been informed by the U.S. military that the accident site was inside the U.S. Marine Corps' Hansen camp, which is used for shooting and landing trainings, near the village. The minister said thorough investigation into the incident is the first priority. "We take safety in our operation very seriously," local media cited a senior officer of the U.S. Forces Japan as saying, adding "that is why we conduct extensive investigations to learn what happened so that we can make our operations as absolutely safe as possible." He did not elaborate on any possible impact of the crash on the Japan-U.S. defense ties. The incident came at a sensitive time when the second batch of 12 U.S. Osprey aircraft is being deployed to the prefecture. On Saturday, two more of U.S. Osprey aircrafts left the U.S. military Iwakuni base in Yamaguchi Prefecture for the Futenma airbase amid strong protests by local people. Okinawa prefectural government and residents have demanded for long to move U.S. bases out of the prefecture, especially the key Futenma airbase, due to safety concern. However, Japan's central government and the United States continued to deploy more U.S. aircrafts to the prefecture, which holds more than 70 percent of U.S. bases in Japan.