"I can confirm that my client has acknowledged complicity in transport," the man's lawyer, Tollef Skobba told Aftenposten newspaper on Wednesday.
Police divers on Tuesday night recovered the dog cage, along with the remains of Kari Grønnestad, who disappeared three years ago aged 59, after carrying out a search in the Skien river.
Kari Grønnestad, 59, disappeared without a trace three years ago. Iit was only on Sunday, when police were called out to the home of her 31-year-old daughter and her partner following a loud row, that he made his grisly accusation.
The woman was arrested on Sunday night along with her partner, who was released on Monday after a ruled that there was insufficient reason to keep him in custody.
The woman's lawyer, Bjorn Nærum, claims that she is surprised by the man's confession and denies having any involvement with her mother's disappearance.
Grønnestad's daughter was the last person to see her mother before she went missing in 2012.
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She then went on to play a prominent role in the search efforts, releasing photos of her mother to the media and begging for clues as to her whereabouts. The search was closed after several months and police never suspected anything criminal had taken place.
“She has always been in despair that her mother has not been found after all these years,” Nærum told VG. “It’s an enormous burden for her to deal with the allegations that she has killed her mother. She strongly denies this.”