Surprise twist after woman accused of holding son captive for 28 years

A relative discovered the woman's son, now 41, inside the "filthy" apartment on Sunday after becoming suspicious and breaking in. Photo / Getty Images, AP

An investigation into a 70-year-old Swedish woman who allegedly held her adult son captive in their apartment for 28 years has thrown up a surprising revelation.

Authorities were called to the apartment after a suspicious relative broke into the flat and found the woman's 41-year-old son locked inside.

The son was taken to hospital after medics found him severely malnourished. He had sores and open wounds covering his legs, had almost no teeth and was struggling to walk and talk.

One of the woman's relatives made the discovery after suspecting she was controlling the boy's life but wasn't sure to what extent.

She broke into the flat while the mother was in hospital for more than a week and discovered the son lying on a blanket on the floor of the kitchen.

The man was found on a blanket in the kitchen that was covered in pus from open sores on his legs, had no teeth left and was also struggling to talk and walk, sources said. Photo / Getty Images

The 70-year-old mother was arrested, but the investigation is now closed after no evidence was found of illegal imprisonment.

The man's injuries could not be attributed to inflicted violence, prosecutor Emma Olsson told Reuters.

"Our forensic investigation of the apartment did not find signs which suggested the man was held there against his will," she said.

"No locked doors or spaces ... or equipment for tying someone up."

The relative who discovered the son said the flat hadn't been cleaned in years and stunk of urine and rotten food.

Rubbish was so piled up in the hallways that it was difficult to walk through.

The relative hadn't seen the boy in more than 20 years.

The woman, who has denied all allegations, was released from custody on Wednesday after three days of detention.

"It's most important now to help both of them and not look for a scapegoat," Olsson said.