U.S. landing craft approach Iejima during the invasion of the small Okinawa island on April 16, 1945. (National Archives and Records Administration)

CAMP FOSTER, Okinawa — Japan is planning a fresh search this fall for a mass grave containing the remains of soldiers killed on Iejima, a small Okinawa island, in the waning days of World War II.

A recovery team from the Ministry of Health, Labor and Welfare will begin excavating an area northeast of Mount Gusuku in October or November, a ministry spokesman said by phone Tuesday.

They are looking for the entrance to a cave complex and the remains of more than 100 Japanese soldiers killed in April 1945.

“Iejima was the scene of fierce battles during World War II,” the spokesman said. “We have been searching for remains on the island for a long time.”

Some government officials in Japan may speak to the media only on condition of anonymity.

Iejima, an elongated, 14-square-mile island approximately three miles off Okinawa’s northwestern coast, is marked by a single mountain peak, 565-foot-high Mount Gusuku.

Smoke rises from Iejima, Okinawa, April 15, 1945, following a naval bombardment. U.S. troops landed on the island the next day. (Naval History and Heritage Command)

Allied bombs started falling on the island in October 1944, but the first U.S. troops landed on April 16, 1945. During six days of heavy fighting, about 2,000 Japanese troops, 1,500 civilians and 200 Americans were killed.

Today, about 4,300 people live on the island, a 30-minute ferry ride from Okinawa.

Information about the potential remains was discovered nearly a decade ago by Kuentai-USA, a Japanese nonprofit dedicated to repatriating World War II remains, founder Usan Kurata said by phone Tuesday.

After years of sorting through records from the U.S. National Archives, the group discovered a document from the 77th Infantry Division that referenced a cave complex about a half-mile northeast of the mountain, Kurata said. The 306th Infantry Regiment reported killing 106 Japanese in the complex between April 15-24, 1945, according to the document.

Kuentai planned to excavate the site, but the ministry stepped in, Kurata said.

The ministry was tipped off to potential locations earlier this year by locals reporting entrances and ventilation ducts, the spokesman said. Its efforts are made more difficult by changes at the site, including postwar construction.

“We searched (for the complex) multiple times in the past but couldn’t find it because the fierce battles changed the geographical features of the island,” the ministry spokesman said.

The cave complex is believed to be 300 feet east of the livestock auction market on the northern side of the island, a spokesman from Ie village’s Welfare Division said by phone Tuesday.

One landowner gave the ministry permission to excavate a 5,000-square-foot tract that may hold one of the entrances to the complex, the ministry spokesman said. The last excavation on the island occurred in fiscal 1986.