According to reports published on social networks, Mahsa Amini had traveled from the western Iranian province of Kurdistan to Tehran to meet relatives when she was arrested on September 13.

Eyewitnesses at the scene told journalists that Amini appeared to have been beaten inside the morality police van while being taken to the detention center, though she was conscious.

A few hours after her arrest, her family was informed that Amini had been hospitalized.

The media center of the Tehran Police Department denied the eyewitness claims of beating Amini, saying she was transferred to one of the police departments in Tehran for "justification and education" about the hijab when she "suddenly suffered a heart problem."

Kiarash Amini, Mahsa's brother, said in an interview with the Iranwire news website that doctors told him they had diagnosed Mahsa as having had either a heart attack or a stroke, "and that while her heart was still beating, her brain is no longer conscious."

Authorities in Iran are increasingly cracking down on women deemed to be in violation of wearing the hijab, which is mandatory in public in Iran. In recent weeks, women judged not to be in compliance have been barred from entering government offices, banks, or riding on public transportation.

The notorious Guidance Patrols, or morality police, have become increasingly active and violent. Videos have emerged on social media appearing to show officers detaining women, forcing them into vans, and whisking them away.

Puran Nazimi, a human rights activist, challenged Iranian authorities to release security camera footage to prove they didn't beat Amini.

The hijab -- the head covering worn by Muslim women -- became compulsory in public for Iranian women and girls over the age of 9 after the 1979 Islamic Revolution.

Many Iranian women have flouted the rule over the years and pushed the boundaries of what officials say is acceptable clothing.

Written by Ardeshir Tayebi based on an original story in Persian by RFE/RL's Radio Farda