TOKYO: A US military chopper made an emergency landing off-base on a small island in Japan's southernmost prefecture of Okinawa, local authorities and media said on Thursday. The incident, which occurred at around 11 p.m. (local time) on Wednesday, involved a UH-1 helicopter with five crew members aboard landing in a field on Tsuken Island due to engine trouble, the US military told the Okinawa prefectural police. No hazardous material was being carried by the chopper and none of the crew were injured in the incident. The emergency landing did not damage the helicopter.