Police raided the apartment in southern Sweden on Wednesday evening after having received a call from a neighbour. Inside, they found the woman and her three children who are now adults. The two youngest have the same father.
According to tabloid Expressen, one of the now adult children managed to briefly leave the apartment in the small town of Bromölla and convince a neighbour to call the police, saying that they had been locked up for over a decade.
"The blinds were always pulled down there and we haven't heard any noise from the apartment," a neighbour told the paper.
Tabloid Aftonbladet had reports from another eye witness. "One of the young women who was led out of the apartment, she could barely walk by herself," the eye witness said.
On Thursday morning, the mother was arrested on suspicion of unlawful deprivation of liberty. She is thought to have kept her three children locked up for over 10 years, according to Expressen, which reported that the mother wanted to keep the children away from her former partner and kept moving to new places when she believed he had found out where they were.
The father told the paper that he agreed not to contact the children when he and the mother broke up around 1998. But soon after the break-up he tried to get in contact with the children.
"I have been looking for my children since the late 1990s," the man said.
Chief prosecutor Pär Andersson told Swedish Radio News that the investigation is at an early a stage and that it is too early to tell if more people were involved.