S. Korean military, UN Command make first joint entry into DMZ mine blast site

South Korean forces and the United Nations Command entered the site of a suspected mine explosion inside the demilitarized zone together for the first time Saturday, five days after the blast on Monday.

The Joint Chiefs of Staff said the two sides conducted a joint operation Saturday to secure access routes and assess the operational environment ahead of a full-scale investigation into the suspected mine blast in the DMZ.

About 20 personnel took part, including members of a JCS joint field investigation TF led by the vice chairman of the Joint Chiefs of Staff, the secretary of the UNC Military Armistice Commission, investigators and operational troops. The team checked overall operational conditions, including route safety assessments and the status of surveillance and communications systems.

Among the operational troops were some soldiers who had participated in the trail-blazing mission on Monday. The JCS said their participation was voluntary. Their inclusion was seen as necessary because the blast occurred along a newly opened section of trail — not an existing patrol route — requiring guidance from personnel familiar with the exact location. The military had previously said it would provide post-traumatic stress disorder support to any soldiers who came forward to help guide the investigation.

Saturday's activity was a preparatory step before the full investigation into the cause of the blast. The military has said the accident site is close to the MDL and near an area suspected of containing North Korean mines, and that the newly blazed trail requires safety measures first — including widening and re-clearing the patrol route and conducting rehearsals for investigation personnel. Officials noted that conditions differ from the 2015 wooden box mine incident involving the 1st Infantry Division, which occurred just in front of a gate along the forward fence line and was wrapped up within six days.

"We have been continuously preparing to ensure a thorough joint field investigation with the UNC while securing the safety of our soldiers," the JCS said. "We plan to thoroughly investigate the cause of the accident and explain the results transparently to the public." It added that it would present the findings of future field investigations objectively and transparently.

Forensic investigation — another key component of determining the cause — is also under way. The military has sent items recovered at the scene, including protective suits, mine-proof overshoes and clothing, to the National Forensic Service for analysis to determine whether the explosive was of South Korean or North Korean origin. Initial results are expected next week. The final assessment will also involve UNC Military Armistice Commission personnel and counterintelligence officials to determine who planted the mine and whether it was intentional.

Based on initial statements, the military said there were two explosions: an Army engineer staff sergeant leading the trail-blazing operation was wounded in the first blast, and the search battalion commander, who moved in to render aid, was injured in the second. Eighteen personnel were deployed in the operation — 15 officers, noncommissioned officers and three enlisted soldiers. Two were seriously wounded, one sustained minor injuries, and the remaining 15 were discharged after thorough medical examinations.

The JCS acknowledged that M14 antipersonnel mines "do not deliver sufficient force when overshoes are worn," but said investigators are keeping all possibilities open — including the chance that the mine was a legacy device that drifted from its original location, given that the blast site is tens of meters from the area suspected of North Korean mine placement and a stream runs nearby.

A UNC inspection of the area suspected of containing North Korean mines will be reviewed after the investigation of the current blast site is completed.