A girl who was vaccinated against cervical cancer died from a malignant tumour of the chest and not from a reaction to the jab, it has emerged.
Natalie Morton, 14, died after being given the injection at the Blue Coat Church of England School in Coventry.
Deputy coroner for Coventry Louise Hunt said the vaccine was not thought to have been a contributing factor.
A pathologist said her undiagnosed condition was "so severe that death could have arisen at any point".
Natalie collapsed less than two hours after being given the Cervarix vaccine on Monday and was pronounced dead at Coventry's University Hospital.
Her death sparked concern among pupils and parents and on Tuesday HPV1 Cervarix vaccinations were temporarily suspended by some schools and primary care trusts.
The deputy coroner, who opened and adjourned the hearing at Coventry Magistrates' Court, said: "It appears that Natalie died from a tumour in her chest involving her heart and her lungs."
The inquest was told that the tumour had "heavily infiltrated" her heart and extended into her left lung.
'Beautiful smile'
Home Office pathologist Alexander Kolar gave the official preliminary cause of death as tumour of the chest.
Natalie's mother Elaine Bullock and stepfather Andrew Bullock paid tribute to her outside the court.
They said she was a "kind and fun-loving teenager with a beautiful smile".
Mr Bullock said: "We now know that Natalie's death was the result of a serious underlying medical condition and most probably nothing to do with the vaccine that she had at school."
Her stepfather said Natalie was "a wonderful daughter, sister and granddaughter".
Mr Bullock added: "We understand that further tests are being carried out to discover the exact cause of Natalie's death."
Natalie's stepfather and mother expressed their gratitude to Blue Coat School head teacher Julie Roberts and her staff, and also thanked paramedics and hospital staff.
"We have seen the flowers and the messages of love and support laid at the cross in the school grounds," her stepfather added.
Cervical cancer vaccination programmes in UK schools were resuming on Wednesday.
It is thought about a million girls have already safely received the Cervarix jab.
More than 1.4 million doses have been given out, of which there have been more than 4,600 suspected reactions reported, according to the Medicines and Healthcare products Regulatory Agency.
The government has said it has great confidence in the safety of its cervical cancer vaccination programme.
Before the preliminary results from the autopsy on Natalie were known, the vaccine's manufacturer voluntarily initiated a recall of one batch of vaccine as a precautionary measure.
But health experts have stressed that the vaccine is safe, estimating the chance of developing a severe, life-threatening reaction to it is around one in a million.
