Elizabeth Thomas: 17-year-old died of stab wound in Oxted
A 17-year-old girl whose body was found in a flat in Surrey, has been named as Elizabeth Thomas from London.
A post-mortem examination found the teenager died of a single stab wound.
A 16-year-old boy who was arrested on suspicion of her murder has been sectioned under the Mental Health Act.
Officers found Elizabeth's body at the flat in Amy Road, Oxted just before 17:20 GMT on Friday. She was from West Wickham, in south-east London and was a sixth-form pupil at Oxted School.
The boy has been transferred to a secure hospital while remaining on bail, Surrey Police said.
Det Ch Insp Claire Pridgeon said it was being treated as "an isolated incident".
In a statement, Elizabeth's school said: "We are deeply saddened and upset by the tragic news about the death of one of our students and we extend our sincere condolences to her family at this very difficult time."
The school said it was offering counselling and support to pupils.
Parents arriving at the school said a special assembly had been organised.
One mother said: "I have a son and a daughter - they are both in complete shock.
"They can't believe that it's happened."