TOKYO (AP) — A shell exploded inside a tank during an exercise Tuesday at a Japanese army training area in southern Japan, killing three soldiers and injuring one, officials said.

The deadly blast occurred when the three soldiers — a tank commander, a gunner and a safety officer — were inside a gun turret on a Type 10 main battle tank during a live fire exercise with two other tanks at the Hijudai Training Area in the southern prefecture of Oita.

The fourth occupant of the tank, the driver, survived but was injured, officials said.

Masayoshi Arai, chief of staff of the Japan Ground Self-Defense Force, said the army has suspended live-fire exercises using Type 10 and Type 90 tanks that use the same shells while officials investigate the cause and other details of the accident.

“We will promptly determine the cause so that we can take preventive measures,” Arai said.

Type 10 is Japan’s newest tank, which it started deploying in 2011.