University of Virginia student Hannah Graham, who last month was found dead in a field near downtown Charlottesville, died from "homicidal violence," the Office of the Chief Medical Examiner in Richmond has ruled.

"The cause of death is homicidal violence of undetermined etiology," the Albemarle County Police Department said Tuesday, referring to a medical term for "causes," USA Today reported.

Police also said a final autopsy report has not been issued and they are still investigating the 18-year-old's disappearance and death.

"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," police said according to USA Today.

Meanwhile, suspect Jesse Matthew Jr. is being held on charges of abduction with intent to defile Graham, who disappeared the morning of Sept. 13 after a gathering with friends. Matthew, 32, was seen with the sophomore at an outside mall in Charlottesville, about 10 miles from where her body was found on an abandoned farm.

The same suspect is being held in connection to the 2005 sexual assault of a woman in Fairfax, Virginia. He pleaded not guilty last week to charges of abduction, sexual penetration with an object and attempted capital murder for the 2005 incident, USA Today reported.

Investigators have also linked Matthew to the death of Morgan Harrington, a Virginia Tech student who vanished in 2009.

As of Tuesday no one has been charged with Graham's death.