and its crew members are under investigation by authorities, they said.
The boat carrying four crewmen was spotted by a South Korean fishing boat in waters south of the Northern Limit Line (NLL) at around 6:50 a.m., according to officials.
The North Korean boat is known to have drifted across the NLL, the de facto maritime border between the two Koreas, due to an engine problem.
The military and the Coast Guard are jointly investigating the incident.
Earlier Tuesday, six North Korean crew members on another fishing boat were found stranded in the East Sea south of the NLL and were sent back home on humanitarian grounds. (Yonhap)