Paris, France - Iran said Friday an investigation into the death in custody of Mahsa Amini found she died of illness rather than reported beatings that sparked three weeks of bloody protests.

Amini, 22, died September 16, three days after falling into a coma following her arrest in Tehran by the morality police for allegedly breaching the Islamic republic's strict dress code for women.

Anger over her death has triggered the biggest wave of protests to rock Iran in almost three years and a crackdown that has killed dozens of protesters and seen scores arrested.

Despite security personnel using lethal force, the women-led protests have continued for 21 consecutive nights, according to online videos verified by AFP.

FILE - A picture obtained by AFP outside Iran on Sept. 21, 2022, shows Iranian demonstrators taking to the streets of the capital Tehran during a protest for Mahsa Amini, days after she died in police custody.

Iran's Forensic Organization said Friday that 'Mahsa Amini's death was not caused by blows to the head and vital organs and limbs of the body.'

The death of Amini, whose Kurdish first name is Jhina, was related to 'surgery for a brain tumor at the age of eight,' it said in a statement.

Amini's bereaved parents have filed a complaint against the officers involved, and one of her cousins living in Iraq has told AFP she died of 'a violent blow to the head.'

Other young women and girls have lost their lives in the protests, but rights group Amnesty International says Iran has been forcing televised confessions out of their families to 'absolve themselves of responsibility for their deaths.'

Iran's judiciary also has denied reports that the security forces killed another teenage girl, Sarina Esmailzadeh, at a rally in Karaj, west of Tehran last month.

Its website quoted a prosecutor as saying an investigation showed Esmailzadeh, 16, had 'committed suicide' by jumping from a building.

Oslo-based group Iran Human Rights said the Esmailzadeh family had come under heavy pressure from government agents to 'force them to repeat the suicide state narrative.'

It said that when the family was asked to identify the teenager's body, 'multiple injuries were clearly visible on her face and the right side of her forehead was completely crushed due to the severity of the blows.'

In a widening crackdown, Iran has blocked access to social media, including Instagram and WhatsApp, and launched a campaign of mass arrests.

A man walk past the fountain of Park Daneshjoo, or Student Park, in the Iranian capital Tehran, reportedly colored red in protest against a deadly crackdown on three weeks of protests sparked by the death in custody of Mahsa Amini, in this UGC image made available on Twitter on Oct. 7, 2022.

Protesters have sought ways to avoid detection, with schoolgirls hiding or blurring their faces while shouting 'Death to the dictator' and defacing images of Iran's supreme leader Ayatollah Ali Khamenei, in verified videos.

Other footage has shown people chanting the protest catch phrase 'Woman, Life, Freedom!' from their apartment windows under the cover of night.

The street violence that ensued across Iran since Amini's death, dubbed 'riots' by the authorities, has led to dozens of deaths, mostly of protesters but also of members of the security forces.

Iran Human Rights says at least 92 protesters have been killed.

A joint letter signed by 21 mainly Iranian human rights groups called on U.S. President Joe Biden to go further to hold Iranian officials to account.

'More urgently needs to be done by the world's leading democratic power to support the people of Iran, discourage further state violence, and address the long history of atrocities and impunity in that country,' the rights groups said.

Despite the government's crackdown, the demonstrations have continued in towns and cities nationwide.

'Death to the dictator,' a group of young women can be heard chanting in the northern city of Rasht in a video posted online Thursday and verified by AFP.

Amnesty has verified the deaths of 52 people killed by the security forces, but says it believes the 'real death toll is far higher.'