An inmate died in an Iranian prison on Saturday, state media reported, as concern mounts about the safety of prisoners arrested during anti-regime protests.

A “limited scuffle” in Iran’s Central Prison of Karaj left one prisoner dead after he was pelted with stones by other prisoners, the state-run Islamic Republic News Agency reported, citing Hossein Fazeli, the public prosecutor of Alborz province.

The clash erupted in a wing for drug offenders, where prisoners also set fire to a number of blankets in the prison yard, Fazeli said, without elaborating on what set the conflict in motion. The prison is on the outskirts of the city of Karaj, some 40 kilometers (25 miles) west of the capital, Tehran.

The violence follows a fire that killed eight inmates in October in Tehran’s Evin prison, where numerous political activists and journalists are jailed.

The incidents have fueled fears for the lives of Iranian prisoners, including thousands arrested in nationwide protests that followed the death in custody of 22-year-old Mahsa Amini in mid-September. She was arrested by for allegedly wearing improper clothes.

The Oslo-based Iran Human Rights said Saturday’s incident in the Central Prison of Karaj, which it said houses some of the detainees of recent protests, started after a man was taken to solitary confinement to be executed. Prisoners smashed closed-circuit cameras and chanted “death to the dictator” and “death to the Islamic Republic,” IHR reported, citing an informed source that it didn’t name.

Separately, the Human Rights Activists News Agency said prisoners clashed with security guards over the imminent execution of four people and more than 100 were wounded from beatings and gunshots.

Also on Saturday, prominent Iranian actress Taraneh Alidoosti was arrested for “publishing material that incited street riots,” the official Islamic Republic News Agency reported.

Rights groups say more than 400 people have been killed in the protests and dozens are facing execution. Islamic Republic authorities this month hanged two men within four days of each other, the country’s first executions in connection with protest.