An official Iranian coroner's report denied Mahsa Amini had died due to blows to the head and limbs while in the custody of Iran's morality police and linked her death to pre-existing medical conditions, state media said on Friday.
The death of 22-year-old Amini while in police custody has ignited three weeks of nationwide unrest marking the biggest challenge to Iran's clerical leaders in years.
Her father has said she suffered bruises to her legs, and has held the police responsible for her death.
The coroner's report said her death was "not caused by any blow to the head and limbs". It did not say whether she had suffered any injuries.
Amini was arrested in Tehran on Sept. 13 for "inappropriate attire", and died three days later.
Referring to the day Amini collapsed in custody, the coroner said she had briefly regained consciousness but that "cardio-respiratory resuscitation was ineffective in the first critical minute, resulting in brain damage".
The report noted pre-existing medical conditions linked to a brain tumor for which she had undergone an operation when she was 8 years old. "She died due to multiple organ failure caused by cerebral hypoxia," it said.
The police, who have enforced strict dress codes since Iran's 1979 revolution, have denied she suffered any harm, previously saying she suffered a heart attack.
Her family deny she had any heart problems.
The government has ordered an investigation into her death.
During the nationwide protests demonstrators have damaged symbols of the republic and called for the downfall of Supreme Leader Ali Khamenei.
Rights groups say more than 150 people have been killed, hundreds have been injured and thousands arrested in a crackdown by security forces.
The government has described the protests as a plot by Iran's enemies including the United States, accusing armed dissidents - among others - of violence in which at least 20 members of the security forces have been reported killed.
State TV broadcast a mass funeral in Tehran on Friday for a member of the Basij - a volunteer militia deployed to quell unrest - saying he had been stabbed by protesters.
'We know our main enemies'
"We know our main enemies. You are novices and mercenaries of Israel, America and Zionism and cannot do anything in this country except torching garbage bins," a woman at the funeral said in comments to state TV, criticizing protesters.
Analysts do not believe the clerical establishment is close to being toppled despite growing frustration over strict social and political limitations imposed over the past four decades since the fall of the US-backed Shah.
The United States has called for accountability for Amini's death "after injuries sustained while in police custody". On Thursday, Washington imposed sanctions on seven Iranian officials over a shutdown of internet access and the crackdown.
Women have played a prominent role in the protests, waving and burning headscarves. High school girls have also taken part.
Meanwhile, the activist rights group HRANA published a statement it said it signed with 161 other rights and feminist groups calling on the United Nations to investigate alleged rights violations in the country.
Iranian media reported on Friday that authorities had denied reports that security forces killed a 16-year-old girl during the protests, citing a chief justice as saying she committed suicide by falling off a roof.
Social media reports and rights group Amnesty International have said Sarina Esmaeilzadeh was killed by security forces when she was struck with batons on the head during protests.
Authorities earlier this week gave a similar cause of death - falling off a roof - for 17-year-old Nika Shakarami, who activists say was killed in Tehran while demonstrating.
