A 17-year-old New Zealander has been found dead in Britain two days after telling her friends she had received frightening calls from a stalker.

Emily Longley grew up in Auckland and attended Westlake Girls High School and Takapuna Grammar.

Her body was found on Saturday morning (UK time) at an address in Bournemouth, southwest England. She had lived in the town with a relative for around eight months.

British police are speaking to a 19-year-old man and say they are urgently seeking witnesses who might have seen any suspicious behaviour.

Emily's father, Mark, says she apparently died in her sleep but the cause of her death remains a mystery.

Friends said yesterday that her parents had encouraged her to go to Britain to study after she left Westlake Girls and fell in with the wrong crowd.

Emily returned to New Zealand for a visit last month, and it seemed as though she had been doing well in Bournemouth, the friends said.

After spending time with family and friends, she returned to England just last week.

On Thursday, she posted on her Facebook profile that she had a stalker. Friends probed further, and she wrote that she had been receiving calls from a private number and was "really scared".

"Someone just called me and i was like whos this? and they were like you dont know me but i know everything about you. and i was like how did you get my number and he was like ill tell you when i see you and kept asking me out. so i hung up and they wont stop calling," she wrote.

The next day, Emily posted that she was "down and out". Twenty-four hours later, she was dead.

Dorset police said in a statement that they were investigating the unexplained death. Officers went to the house at Queenswood Ave, Bournemouth, at 9.55am (UK time).

Detective Inspector Neil Devoto, the senior investigating officer, said a 19-year-old Bournemouth man was "helping officers with their inquiries".

"I am appealing for anyone who witnessed anything suspicious or unusual in the area either this morning or during last night, and anyone who has any information regarding this incident, to contact police urgently," Mr Devoto said.

Friend Hannah O'Gilvy, said last night that she could not come to terms with losing someone so close.

"I need her so badly right now and she's gone. I just wish I could have been there for her. I want her to come back. I wish she didn't go to England."

Hannah said they had shared many dreams, including that they would move to America, where Emily would model while she styled her hair, or they would work at supermarkets and sleep together in a van.

After Emily moved away, the best friends took to chatting over Skype about all the good memories they had shared, Hannah said.

"Everyone's going to remember her. She's so loved. She's such a crazy, wild person."

Hannah said a group of friends were planning to get together to say goodbye to Emily once her body was returned to New Zealand.

She said she would continue caring for her friend.

"I love her and I won't stop."

More than 100 messages had been left on Emily's Facebook page by last night wishing she would rest in peace.

Mark Longley wrote that his daughter had apparently died in her sleep but he did not know how.

"It is a huge shock to us, and Caroline [Ms Longley's mother] and I are going to England to try and find out what happened," he said.

"She was a beautiful girl and full of life, it is so tragic."