The report obtained by The Associated Press shows that a coroner could not determine what killed the woman, whose skull was found in the sex offender's Cleveland home.
The report was released Monday by the Cuyahoga County coroner's office and shows that 25-year-old Le'Shanda Long died of homicidal violence.
Her skull was found in a pink plastic bucket in the basement of Anthony Sowell's home in November. The rest of her remains have not been found.
The report says that the skull was intact but that the bucket had bite marks around the rim that weren't made by a person.
Autopsies released last week for the other 10 victims showed most were strangled with household objects.
Sowell has pleaded not guilty to killing the 11 women and hiding their remains in and around his home.
A CBS News investigation uncovered exclusive details revealing critical mistakes by police and prosecutors working the case - how they could have stopped a serial killer if they hadn't ignored charges of rape.
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