The six men, whose ages are between 27 and 67, were handed over to South Korean authorities in the neutral border village of Panmunjom, The New York Times reported.
The South's Unification Ministry said it would question the men on how and when they had arrived in North Korea, as it is illegal for South Koreans to enter the North without government permission under the South's National Security Act.
"Seoul has verified overnight that all six are citizens, but because the North claimed they voluntarily crossed over into the North, it has been determined that their actual names will not be released until they have been questioned," said ministry spokesman Kim Eui-do.
The ministry said Thursday that the six men were not on its list of people abducted by the North, South Korea's Yonhap News Agency reported.
In 2010, the North's media reported that it detained four South Koreans who entered the country illegally.
"The men who are coming home may be the same as the ones mentioned in 2010, but because the North never identified those people by name at the time, there is no way to tell for certain until they are questioned," Kim said.
Selena Gomez drops F-bomb, walks off stage during Jingle Ball performance
'SNL': 'Anchorman 2' cast, One Direction sing 'Afternoon Delight' [VIDEO]