Authorities say the two men had killed 16 fellow fishermen on their boat and then fled to South Korea.

South Korea said Thursday it expelled two men from North Korea after learning they murdered 16 crew members on their fishing boat before fleeing to the South.

The pair, both in their 20s, were questioned by South Korean authorities after being found on Saturday near the maritime border in the East Sea, also known as the Sea of Japan.

The investigation concluded that the men had killed 16 fellow fishermen on their boat and then fled to South Korea, Seoul’s unification ministry said.

The two men were deported to the North via the truce village of Panmunjom on Thursday after informing Pyongyang of the plan, ministry spokesman Lee Sang-min told reporters.

“If they had been incorporated into our society, it was judged they would pose a threat to the lives and safety of the people,” Lee said.

Details of the killing or the boat’s whereabouts were not provided.

More than 30,000 North Koreans have escaped from the reclusive state to the South since the two were separated by war more than 65 years ago, according to government data – many driven by prolonged economic hardship.

The defectors are interrogated by South Korean intelligence authorities upon arrival and spend about three months in a government-run facility for re-education before they are discharged into society.