The 16-year-old girl, her short black hair uncovered, entered a subway car in Tehran early Sunday on her way to school, security camera footage broadcast by Iran’s state television showed. Minutes later, she was dragged out unconscious and laid on the train platform.

All week, the girl, Armita Geravand, has been in a coma, guarded by security agents in the intensive care unit of a military hospital in Tehran and evoking broad comparisons with Mahsa Amini, who died last year at 22 in the custody of the morality police after being accused of violating Iran’s hijab rules, which require women to cover their hair.

Exactly what happened to Armita on Sunday is not clear, and the government has not released footage from inside the train that would reveal what made the teenager collapse.

But the news of another young woman in a coma under murky circumstances — another girl, another metro station, another hospital, another grief-stricken family — was enough to stir outrage in Iran and fuel accusations that the government’s hijab agents must have harmed her.

Ms. Amini’s death last year set off a nationwide uprising, led by women and girls, demanding an end to Iran’s clerical theocracy. The “Mahsa movement,” as it was called, morphed into the most serious challenge to the legitimacy of the ruling clerics since they took power in 1979. In crushing the protests, the government killed more than 500 people, including teenagers and children, and arrested tens of thousands of demonstrators.

Farzad Seifikaran, a journalist with Radio Zamandeh who first reported the story about Armita on Sunday, interviewed two of her relatives, a friend and another person familiar with the episode. The sources told him that Armita and two of her friends, who were also not covering their hair, argued with officers enforcing hijab rules, Mr. Seifikaran said, and that one of them pushed Armita.

She fell and hit her head on a metal object on the train and suffered cerebral hemorrhaging, Mr. Seifikaran said the sources told him.

The government says she fainted because of a drop in blood sugar after skipping breakfast. Masoud Dorosti, head of the Tehran Metro Operating Company, told the Iranian news media that footage from its cameras showed no sign of a verbal or physical confrontation between passengers and municipality employees.

The state news agency, IRNA, published a video of Armita’s parents looking shellshocked and repeating the government narrative. “My daughter, I think her blood pressure, I don’t know what, I think, they say that her blood pressure dropped then she fell down and her head hit the edge of the metro,” said her mother, Shahin Ahmadi, stumbling on her words as her voice shook.

Her father, Ahmad Geravand, looked down, arms folded, as she spoke. Mr. Geravand said Armita had been healthy and did not use any medications, and he asked for prayers for her.

Armita lives in a working-class neighborhood of western Tehran and is an art student at a vocational art and design high school, her classmate and relatives told Mr. Seifikaran. She has a passion for painting and pursued taekwondo training semiprofessionally, they said.

The government’s lack of openness and the tight security at the air force hospital have contributed to the suspicions that the authorities had a hand in harming Armita. Anger has spilled out this week on social media, with people denouncing what they see as the government’s brutality.

“Transparency means all the security agents leave Fajr Air Force Hospital and surrounding areas and journalists be allowed to report on what happened to the 16-year-old girl,” wrote Mohsen Borhani, a lawyer in Tehran, on X, the social media platform formerly called Twitter.

The authorities eventually stifled street protests over Ms. Amini’s death, and they violently squelched commemorations of its anniversary last month. But sporadic small protests still erupted in several cities, with people chanting, “Death to the dictator.”

Many women and girls across Iran have continued to defy the mandatory hijab rule by letting their hair show in public. This collective act of civil disobedience has been risky, as the government has come up with new ways to catch and punish such women, including the use of facial recognition software.

A group of Iranian teachers’ unions said in a statement on Wednesday that the Education Ministry’s security director had visited Armita’s high school and warned teachers and staff that they would be fired if they spoke about her, and that her classmates were threatened to keep them silent.

Security agents have swarmed the hospital, locked down the ward where Armita is kept and threatened to arrest family members and her classmates if they spoke to the news media, according to rights groups and activists. Maryam Lotfi, a journalist for the daily newspaper Shargh who went to the hospital on Sunday, was arrested as she was interviewing Armita’s mother and detained for 24 hours, according to her colleagues and editors.

“We can confirm that Armita’s family is under immense pressure to adhere to the state’s narrative, while she lies unconscious and guarded by state security personnel in a military hospital with all visitors banned,” said Jasmin Ramsey, deputy director of the Center for Human Rights in Iran, an independent advocacy group based in New York. “If her case were as straightforward as they claim, why all the restrictions and secrecy?”

In Iran, parents of teenage girls are once again anxious about their safety. During the uprising last year, Iranian security forces systematically targeted not only adults but teenagers and children who were staging a revolt in schools, launching raids that intimidated students and detaining up to 1,000 minors.

Many parents and students were already fearful because of another unexplained trauma: Hundreds of schoolgirls in dozens of cities were hospitalized early this year with respiratory and neurological symptoms that the authorities said were partly caused by deliberate attacks with toxic chemicals.

“As a mother, I am feeling very stressed these days,” said Fariba, 46, whose daughter is a student in Karaj, near Tehran, and who asked that her last name not be published out of fear of retribution. “I cannot let my daughter leave the house alone; I am afraid that something bad would happen to her. She does not want to wear a hijab. So many of our girls these days have become extremely brave.”

The plight of Iran’s women and their courage in pushing for their rights have reverberated widely, both within the country and abroad. Germany’s foreign minister, Annalena Baerbock, was among those reacting to the news about Armita, posting Wednesday on X, “Once again a young woman in Iran is fighting for her life.”

“Shocked and concerned about reports that Iran’s so-called morality police have assaulted 16-year-old Armita Geravand,” Abram Paley, the U.S. deputy special envoy on Iran, wrote on X. “We continue to stand with the brave people of Iran and work with the world to hold the regime accountable for its abuses.”

Iran’s foreign ministry spokesman, Nasser Kanaani, responded to the Western criticism on Thursday, posting on X a rejection of “interventionist & biased remarks” and “insincere concern over Iranian women & girls.”

Leily Nikounazar contributed reporting from Brussels.