Mexico City A South Korean presidential official has pledged a prompt and thorough investigation into recent explosions in the Demilitarised Zone (DMZ) that injured three South Korean soldiers. The official, speaking to reporters in Mexico City while accompanying President Lee Jae Myung on his state visit, said an objective investigation was under way. Forensic analysis of fragments collected from the site is being conducted to determine whether the suspected mines were of South or North Korean origin. The official said investigators must establish whether the explosions were caused by mines, identify their type and determine whether they were planted by North Korea. If North Korea was not responsible, investigators would examine what caused the explosions. The probe is being conducted in coordination with the United Nations Command because the location is part of a newly established reconnaissance route and remains dangerous to access. The explosions occurred on Monday and injured three South Korean military personnel. Speculation has grown that the blast may have involved a landmine allegedly placed by North Korea on the South Korean side of the DMZ, although authorities have not confirmed the cause. South Korea’s new Defence Minister Kang Shin-chul on Tuesday called on North Korea to stop strengthening its border defences. He said such activities could have secondary effects and that the explosion could potentially be connected to them. Kang also said South Korea’s military had not yet established whether the blast site matched an area where North Korea was suspected of laying mines across the border. He explained that investigators needed to determine whether the minefield, patrol route and explosion site were the same location. The minister said difficult terrain and poor visibility had made it difficult to obtain clear footage from the area. Investigators may have to rely partly on accounts from personnel who were present. The presidential official ruled out any possibility of a cover-up and said authorities would work to complete the investigation quickly and announce the findings.