Japan’s coast guard said what appeared to be wreckage from the tilt-rotor V-22 Osprey and one “non-responsive” person had been found some three kilometres from Yakushima island.

Fishing boats in the area found three people in the surrounding waters, a representative of a local fisheries cooperative said, adding their condition was unknown.

Another Osprey landed safely at the island’s airport on Wednesday afternoon around the time of the crash, a spokesperson for the local government said. US forces in the region were still gathering information, a spokesperson said.

The United States, which pledged to defend Japan after its defeat in World War II, has about 54,000 US troops in the country, many in the strategically important southern island chain, amid growing Chinese military assertiveness in the South China Sea.

The crash happened just before 3pm with witnesses saying the aircraft’s left engine appeared to be on fire as it descended, media reported. Japan, which also operates Osprey aircraft, said on Wednesday it had no plans to ground the aircraft but had asked the US military to investigate the crash.

Developed jointly by Boeing and Bell Helicopter, the Osprey can fly both like a helicopter and fixed-wing aircraft and is operated by the US Marines, US Navy and the Japan Self Defence Forces.

The deployment of the Osprey in Japan has been controversial, with critics saying it is prone to accidents. The US military and Japan say it is safe.