Alisa Dmitrijeva, the 17-year-old Latvian whose remains were found by a dog walker on the Sandringham estate on New Year's Day, is likely to have been killed in September, according to police.
The teenager from Wisbech was last seen alive in King's Lynn on 30 August. Police are concentrating their investigation on the week leading up to 6 September. Investigators believe she died within days of her disappearance.
Quoted by the Press Association, Detective Chief Inspector Jes Fry said that his team was carrying out "more focused inquiries to establish what happened to her".
"We particularly want to speak to anyone who may have seen Alisa between midday on 30 August and midnight on 6 September," he said.
"We know she was in both the King's Lynn and Wisbech areas during this time, and want to hear from anyone who has any information about her whereabouts over the eight days."
The last confirmed sighting of Dmitrijeva was by two men known to have picked her up in a P-registered green Lexus on 31 August. During an interview, the men, who police describe as acquaintances of the victim, said they dropped her off later that evening at Asda in Wisbech.
"She clearly knew these men and trusted them," said Fry. "We believe she got into the car voluntarily," however Fry dismissed speculation that the victim had a drug habit or worked in the sex trade.
Norfolk Police released a statement detailing the victim's background. It read: "She enjoyed a party lifestyle and spent time at internet cafes and parks when not at home... she enjoyed swimming outside and make-up, the latest fashions and going out with friends. She was a really confident girl with many friends."
Dmitrijeva, who moved to the UK with her family in 2009, was due to start at the College of West Anglia in King's Lynn last September.
Police, who used DNA profiling and a palm print to identify the remains, are also investigating reports that Dmitrijeva had a boyfriend, as well as appealing for anyone that held or attended a function on the estate in early September.
"There are thousands of visitors to Sandringham and we want to prioritise those who were involved in events in the area and then work our way through people who may have attended those events and may have seen something," said Fry.
"We particularly want to speak to people within the Latvian, Lithuanian and Russian communities in the areas, and are working with local groups and individuals who may be able to assist."
The victim's family released a statement that read: "We are devastated by the news of Alisa's death. We wish to grieve in private."
According to police, the royal family have been kept informed about the investigation.