The whereabouts of the colleagues of 13 North Korean defectors who worked at a restaurant in China have not been confirmed as they do not appear to be under Seoul's protection, a source said Thursday.

Last week, a group of North Korean restaurant workers defected to South Korea en masse amid toughened international sanctions on Pyongyang over its latest nuclear and missile tests.

There has been speculation that about five to seven other North Koreans who worked at the same restaurant in the Chinese eastern port city of Ningbo are hiding in China under the South government's protection.

"As far as I know, there are no remaining North Korean workers hoping for defection to the South," said a source familiar with North Korea. "It seems that there are no such people under the South Korean government's protection."

No confirmation of their whereabouts raises the chance that they may have been repatriated to North Korea, experts say.

North Korean restaurants in foreign nations have recently faced business hardships with some shutting down following stronger sanctions. They have served as one of the main sources of dollars for cash-strapped North Korea, which is suspected of using such earnings to bankroll its nuclear and missile programs.

Seoul's unification ministry declined to comment on the whereabouts of the remaining colleagues.

"We cannot say anything about the issue as relevant questioning (by authorities on the 13 defectors) is under way," said a ministry official. (Yonhap)