A 14-year-old girl from Hove who died on her first day back at school did not die from an allergic reaction to nuts.
She was taken the short distance from her school to the Royal Sussex County Hospital but died in the accident and emergency department.
Sussex Police officers are investigating the death of Brighton College pupil Naishel Kelly on behalf of the coroner after post-mortem tests ruled out anaphylaxis.
The force said: “The death is being treated as unexplained but is not regarded as suspicious.”
Naishel suffered breathing problems, possibly an asthma attack, last Tuesday (3 January) and was initially treated at school by a nurse and paramedics from the South East Coast Ambulance Service.
She was taken the short distance from her school to the Royal Sussex County Hospital but died in the accident and emergency department.
Sussex Police said: “The family are naturally devastated about the loss of their daughter and are trying to come to terms with the sudden tragic loss of their elder child.
“A post-mortem (examination) took place on Thursday 5 January and further forensic tests are being carried out to establish the cause of death.
“Results are not likely to be known until later this month.
“However, one thing we can say is that it is already clear that eating a biscuit was not a factor in Naishel’s tragic death.”
Friends have been leaving tributes on a Facebook page.
Brighton College headmaster Richard Cairns said that everyone at the school was devastated by Naishel’s death.
He said that their thoughts were with her family, Kian, 7, and parents Ian and Mariles.