The Defense Ministry has sent a telephone message to North Korea following the death of a South Korean man killed by a wooden box land mine found on the Imjin River that is thought to have come from North Korea.

A ministry official says the message asking the North to take measures to prevent a recurrence was sent via the Yellow Sea military communication line around 5 p.m. on Sunday.

South Korea’s Joint Chiefs of Staff says the wooden box land mine seems to have originated from the North but was likely not sent intentionally.

A number of the mines have been found on the river near the North Korean border and are thought to have washed downriver following heavy seasonal rains.

On Saturday, a 48-year-old man was pronounced dead at the scene, and a 25-year-old man was hospitalized for injuries from the explosion of the wooden box land mine, which is designed to explode when opened.

Police say the two men were likely carrying the land mine they found while fishing illegally at a restricted area of the Imjin River when it exploded.