A South Korean fisherman who defected to North Korea but was returned to the South on Monday is being questioned by authorities.

Hwang Hong-ryon returned to Sokcho port in Gangwon Province aboard a North Korean patrol boat Monday afternoon. The North Korean vessel also handed over Hwang's three-point-nine-ton ship to two South Korean maritime police patrol boats at the eastern sea border, five days after he crossed the sea border.

A joint questioning team made up of National Intelligence Service officials, military personnel and the police, is considering whether to apply the National Security Law and the Maritime Traffic Safety Law in the investigation of the case.

The 57-year-old fisherman sailed his boat out of the port Wednesday without permission from authorities and went to the North, apparently under the influence of alcohol.