HONG KONG — Five United States Marines were missing and two have been found after two aircraft crashed off the coast of Japan early Thursday, the Marine Corps and the Japanese military said.

The crash is the latest in a growing number of American military aircraft accidents in recent years and follows increased scrutiny of operations in Asia, where American warships were involved in two deadly collisions in 2017.

In a statement from the Marine base in Okinawa, officials said that two Marine aircraft, a KC-130 Hercules and an F/A-18 Hornet, were involved in the accident about 200 miles off the coast of Japan around 2 a.m.

The aircraft had taken off from a base at Iwakuni, in southern Japan, and were “conducting regularly scheduled training when the mishap occurred,” the statement said. It provided few details, saying only that the circumstances were under investigation.