A 70-year-old woman is suspected of having kept her 41-year-old son locked up, reportedly for 28 years, in an apartment in the south of the Swedish capital Stockholm, police said on Tuesday.
The head of the preliminary investigation said that the woman was held on suspicion of unlawful deprivation of liberty and grievous bodily harm, according to news agency the Associated Press.
According to a report in a Swedish newspaper, the man's apparent captivity had started 28 years ago, which would have made him 13 at the time.
The official said that the 41-year-old son was found by a relative who then alerted authorities.
Denying any wrongdoing, the accused woman said that the son was admitted to a hospital to be treated for "the physical injuries he had when he was found", the official said.
"We cannot go into what type of injuries" he has, the official said.
AP quoted Swedish newspaper Expressen as saying that the man was found on Sunday by a relative who had learned that the elderly woman had been admitted to a hospital. The relative went to the flat, found the main door unlocked and entered it.
Recalling what she had witnessed, the relative said that there was "urine, dirt and dust" all over the place and "it smelled rotten."
She heard a noise from the kitchen and found the man sitting on blankets and pillows. According to the relative's account in the paper, he had no teeth, had sores on his legs and his speech was slurred.
"He spoke very fast and a little incoherently, but he was not afraid of me," the relative was quoted as saying by Expressen.
The official said that investigators would be interviewing the mother, the son and witnesses.
(With inputs from AP)