The South Korean military on Thursday said it had fired warning shots as North Korean soldiers approached the border allegedly in search of their comrade who is believed to have defected, AFP reported. This is the second report of defection in two months.

South Korea’s defence ministry said its soldiers had fired around 20 warning shots at the North Korean troops near the border.

On Thursday morning, surveillance equipment detected a low-ranking soldier crossing the border despite heavy fog, South Korea’s Joint Chiefs of Staff spokesperson Roh Jae-cheon said, according to Reuters. “Our military secured his safety, and a questioning will be conducted by related agencies to find out the background of his defection and motive, etc,” he said.

Thursday’s defection was the fourth by North Korean soldiers through the demilitarised zone in 2017, according to AFP. On November 13, a North Korean soldier was critically wounded after being shot at while he was trying to flee to South Korea. He is currently being treated near Seoul. Doctors had earlier said they had removed a a 10.6-inch long parasitic worm from his digestive tract.