The North Korean man who was taken into the South Korean military’s custody near the Civilian Control Line on Monday was found to have swum his way to the South wearing a diving suit and fins. 

The Joint Chiefs of Staff(JCS) made the revelation on Wednesday, saying the man is likely to have reached the coast near the Unification Observatory and passed through a drainage tunnel located at the bottom of an iron fence on the inter-Korean border.

The man, in his 20s, is said to have conveyed his intent to defect during questioning.

The JCS said, in particular, that the man was spotted several times on military surveillance cameras once he made his way out of the water, but the military failed to take proper measures. The JCS also said it found faults in blocking the drainage tunnel.

The JCS said it takes the situation gravely, adding that it is conducting an on-site investigation with the command headquarters for ground forces. It said it will devise follow-up measures in line with the results.