TOKYO (AP) — An initial analysis of flight data recorders recovered from the crash of two Japanese navy helicopters showed no sign of mechanical problems, Japan’s defense minister said Monday, indicating likely human error. One of the eight crew members died and a search is continuing for the seven others.

Defense Minister Minoru Kihara said an initial analysis of data from the two flight data recorders on each helicopter showed no abnormality during their flight and that mechanical failure was most likely not the cause of the crash.

The two SH-60K reconnaissance helicopters from the Maritime Self-Defense Force lost contact late Saturday during nighttime anti-submarine training near Torishima island, about 600 kilometers (370 miles) south of Tokyo, officials said.

A crew member who was recovered early Sunday from the water was later pronounced dead. Searches continued Monday for the seven who were still missing, along with the fuselage of the aircraft. The seabed at the crash site east of Torishima is about 5.5 kilometers (3.4 miles) deep and the recovery is considered a challenge.