Noel Brown,69, and his daughter Marie,41, died in his southeast London flat on Monday.
Police believe there is a "strong possibility" that Marie disturbed the attackers as they tried to dismember his body.
The deaths were discovered at Mr Brown's flat in New Butt Lane, Deptford at around 2.45am on Monday.
Detectives are trying to establish why they were killed and Detective Superintendent Paul Monk said Mr Brown's conviction in 1999 for a sex offence that saw him jailed for four years was not "screaming out" as a motive.
He said there had been nothing in Mr Brown's life in the 18 years since the conviction to suggest this was a motive to murder him.
Mr Monk said: "The offence was a sex offence, he was convicted and served time and was released in 2004 but I'm not prepared to give any more details."
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