South Korea said Saturday it will request North Korea to further investigate the killing of a South Korean government official who was shot by North Korean troops after being found adrift near the rivals’ disputed sea boundary while apparently trying to defect, AP reported.

Seoul could also possibly call for a joint investigation into Tuesday’s shooting, which sparked outrage in the South and drew an apology from North Korean leader Kim Jong Un.

However, the North Korean message, which was announced by the office of South Korean President Moon Jae-in on Friday, largely passed the blame for the shooting to the South Korean official, claiming that he refused to answer questions and attempted to flee before North Korean troops fired at him.

South Korean officials during a presidential National Security Council meeting Friday evening concluded that further investigation was needed because the North’s account of the incident was different from what was gathered by South Korean intelligence, Moon’s office said.

“We have decided to request the North to conduct an additional investigation and also request a joint investigation with the North if needed,” the Blue House said in a statement. It said the South will also “swiftly take measures to further strengthen surveillance posture” in waters off the country’s western coast to prevent similar incidents.

South Korea’s coast guard was deploying dozens of vessels and hundreds of officers to search waters near the western sea border Saturday for the official’s remains.