A South Korean Navy maritime patrol aircraft crashed during a training mission on Thursday, killing all four crew members on board.

According to a report by South Korea’s Yonhap News Agency, the P-3 maritime patrol aircraft went down in a mountainous area near the southeastern city of Pohang at approximately 1:49 p.m. local time.

The Navy stated that the aircraft had taken off from a Pohang airbase at 1:43 p.m. for a takeoff and landing training exercise. Just six minutes later, it crashed for reasons that remain unknown.

All four people aboard—two commissioned officers and two non-commissioned officers—were killed. Their bodies have been recovered, but their identities have not yet been publicly disclosed.

Eyewitnesses reported seeing smoke rising from the mountain and hearing the sound of an explosion.

A Navy official noted that the aircraft was usually stationed with a naval unit on Jeju Island but had been deployed to Pohang for the training exercise.

In response to the crash, the Navy has grounded all P-3 patrol aircraft and launched an investigation to determine the cause of the incident. No civilian casualties have been reported.

The South Korean Navy operates 16 P-3 aircraft, widely known for their anti-submarine capabilities and nicknamed “submarine killers.” The crashed aircraft was one of eight P-3CK models refurbished by Korea Aerospace Industries. This marks the first crash involving a South Korean Navy P-3 aircraft.