University of Virginia student Hannah Graham, whose remains were found last month on a vacant property in Albemarle County, Virginia, died from “homicidal violence,” authorities revealed Tuesday night.
How Graham, 18, was killed, however, remains “undetermined.”
“We have received the cause and manner of death from the Office of the Chief Medical Examiner in the Hannah Graham investigation,” the Albemarle County Police Department said in a statement to PEOPLE.
“A final autopsy report has not been issued. The cause of death is homicidal violence of undetermined etiology. The manner of death is homicide.”
This is the first time police have called Graham’s death a homicide.
Graham, a sophomore, vanished in the early hours of Sept. 13 in Charlottesville, Virginia. She was seen on surveillance videos wandering in a pedestrian mall near the university after a night out with friends.
Police found her remains on Oct. 18 in rural Albemarle County – five miles from where she had last been seen.
On Sept. 24, police arrested Jesse Leroy Matthew, Jr., 32, the last person believed to have been seen with her, on charges of abduction with intent to defile. Matthew is scheduled for a preliminary court hearing on Dec. 4 in Charlottesville.
Authorities say DNA evidence also linked Matthew to a 2005 sexual assault in Fairfax, Virginia. On Friday, he pleaded not guilty to felony counts related to the attack.
He has also been linked to the 2009 disappearance and death of Virginia Tech student Morgan Harrington, 20.
The Albemarle County Police Department and the Albemarle County Commonwealth’s Attorney “remain committed to the investigation,” Albemarle County police said in the statement. “To protect the integrity of the case, we will not be answering questions or releasing additional information. We are working hard to ensure that justice is served.”