British police have opened a murder investigation after the body of a woman was discovered on Queen Elizabeth II's Sandringham estate in Norfolk, England.

The body was found in the forest of the estate, about three miles from the house, on Jan. 1 by a dog-walker. Now on day four of the investigation, police are saying that the girl could have been murdered.

The circumstances suggest this is a murder case and we are looking at missing persons reports and cold cases both locally and nationwide, Detective Chief Inspector Jes Fry said Tuesday.

“We are at the very early stages of the investigation and it could be a complex inquiry,” Fry added. “The body had been there for some time.”

An autopsy was conducted on Tuesday and there was no evidence of accidental injury, damage due to firearms or bladed weapon, according to the BBC. Police added that they are analyzing DNA samples in an attempt to identify the woman.

The body was described as a young, white, adult female, aged between 15 and 23-years-old, which has been at that site for a period estimated to be between a month and up to four months, and police are already looking to connect it to a pair of missing persons cases.

Latvian-born Alisa Dmitrijeva, a 17-year-old living in Wisbech, Cambridgeshire, and Lithuanian Vitalija Baliutaviciene of Peterborough, 29, both went missing in August.

We will be focusing on all local missing persons and then spread our catchment area depending on how our investigation goes, Fry told The Daily Mail.

Part of the post-mortem will try to establish the identification through fingerprints or DNA which may help us identify who the victim is more quickly.

Hopefully in the next day or so, we will have a good idea who we are dealing with and that may open fresh lines of inquiry.

Buckingham Palace has not commented on the body. Queen Elizabeth and her husband, Prince Philip, were at the Sandringham estate when the body was discovered.

Generations of British royals have used the Sandringham residence, starting with Queen Victoria in 1862.