Lim Ji-hyun escaped the communist state in 2014 and became a popular TV personality in the South. She has turned up in Pyongyang in a recently released video saying she returned of her own free will.
South Korea is investigating the case of a North Korean defector who became a celebrity refugee in Seoul. She recently appeared on Pyongyang television claiming she had returned home from the "hell" of the capitalist South.
Lim Ji-hyun, a female defector in her twenties, arrived in Seoul in 2014 and soon became a public figure after starring in several South Korean TV shows featuring escapees from the North.
But on Sunday Lim abruptly appeared in a video on the North's propaganda network, describing how her "fantasy" about the wealthy South had been shattered.
TRT World's Joseph Kim reports from Seoul.
In the video, posted on the North's Uriminzokkiri website, Lim says she had "returned home" last month and was now living with her family in the western city of Anju.
It is unclear whether Lim returned voluntarily, with South Korean media speculating that she might have been kidnapped at the Chinese border with the North while trying to reunite with her family.
Police sources who probed Lim's home and financial accounts in Seoul told the South's JoongAng Ilbo daily there was little sign of her trying to wrap up her life in the country and move elsewhere.
"Relevant authorities are investigating the North Korean defector Lim Ji-hyun," said Lee Yoo-jin, deputy spokeswoman of Seoul's unification ministry handling North Korea affairs.
Seoul's spy agency declined to comment.
In the video, Lim identified herself as Chon Hae-Song, which she said was her real name in the North.
Wearing a traditional silk hanbok and a red badge bearing the images of the North's two former leaders, Kim Il-Sung and Kim Jong-Il, Lim tearfully detailed her "miserable" life in the capitalist neighbour where "money is all that matters."
"I went to South Korea harbouring this fantasy that I would able to eat and live well and make a lot of money there, but the South was not the place I imagined," she said, adding she had wanted to become an actress in Seoul.
"Every single day in the South was like hell. Every night, I cried thinking about my motherland and my parents in the North," she told her interviewers.
Lim also accused a South Korean TV station of pushing her to lie about her life in the North to make it sound more miserable than it actually was.
"Everything I said on TV was scripted to make North Koreans look barbaric, ignorant and stupid," she said, describing herself as "human trash" for defaming her motherland.
Other defectors who have reappeared in the North have been displayed on similar programmes, prompting speculation they had been kidnapped or coerced into returning by threats to their families to serve Pyongyang's propaganda.
More than 30,000 North Koreans have fled poverty and repression in the isolated homeland and settled in the South.
But many complain of lack of opportunities, discrimination and difficulty in adjusting to the cut-throat, ultra-competitive society.
A recent survey showed more than 60 percent of defectors consider themselves "low-class citizens," with the average suicide rate among them at 15 percent, nearly three times the South's national average, which is already the world's highest.
Lee So-Yool, another North Korean defector and TV celebrity in Seoul, however, said Lim would have been broadcast criticising the South regardless of whether she had returned to the North voluntarily or forcibly.
"She has to do it once she is back in the North. She has no choice in order to survive," Lee said during a live YouTube broadcast on Monday.