SEOUL, South Korea (AP) — North Korea accused South Korea of sending ships across the disputed sea boundary to find the body of a South Korean official recently killed by North Korean troops, warning Sunday the intrusion could escalate tensions. South Korea denied the accusation. Along with its denial, South Korea proposed a joint investigation to resolve discrepancies in each country’s account of the South Korean official’s death last week. Officials in Seoul have said the 47-year-old was likely attempting to defect before North Korean troops aboard a boat fatally shot him and burned his body. According to Seoul, North Korea on Friday sent a message including a rare apology by leader Kim Jong Un for the shooting death of the official, who was found floating on an object in its waters.