A high-rise building in Tehran engulfed by a fire collapsed on Thursday, killing at least 20 firefighters, Iranian state television quoted the city's mayor as saying on Thursday.
"At least 20 firefighters who were trapped under rubble have died," Mayor Mohammad Baqer Qalibaf said. "They are martyrs. They lost their lives when trying to help people."
Qalibaf had earlier said around 25 firefighters were trapped inside the building. State TV said the death toll might increase.
The disaster struck the Plasco building, an iconic structure in central Tehran just north of the capital's sprawling bazaar. Firefighters, soldiers and other emergency responders dug through the rubble, looking for survivors.
Iranian authorities did not immediately release definitive casualty figures, which is common in unfolding disasters.
Iran's state-run Press TV announced the firefighters' deaths, without giving a source for the information. Local Iranian state television said 30 civilians were injured in the disaster, while the state-run IRNA news agency said 45 firefighters had been injured.
Firefighters battled the blaze for several hours before the collapse. The fire appeared to be the most intense in the building's upper floors before the collapse. Those floors were home to garment workshops where tailors cook for themselves and use old kerosene heaters for warmth in winter.
Police tried to keep out shopkeepers and others wanting to rush back in to collect their valuables.
Tehran's mayor, Mohammad Bagher Ghalibaf, said there were "no ordinary civilians" trapped under the rubble. However, witnesses said some people had slipped through the police cordon and gone back into the building.
IRNA reported that Iranian President Hassan Rouhani ordered Interior Minister Abdolreza Rahmani Fazli to investigate and report the cause of the incident as soon as possible.
He also ordered the ministry to take care for the injured and take immediate action to compensate for those affected by the disaster.
The building came down in a matter of seconds, shown live on state television, which had begun an interview with a journalist at the scene. A side of the building came down first, tumbling perilously close to a firefighter perched on a ladder and spraying water on the blaze.
A thick plume of brown smoke rose over the site after the collapse. Onlookers wailed in grief.
Among those watching the disaster unfold was Masoumeh Kazemi who said she rushed to the building as her two sons and a brother had jobs in the garment workshops occupying the upper floors of the high-rise.
"I do not know where they are now," Kazemi said, crying.
In a nearby intersection, Abbas Nikkhoo stood with tears in his eyes.
"My nephew was working in a workshop there," he said. "He has been living with me since moving to Tehran last year from the north of the country in hopes of finding a job."
Jalal Maleki, a fire department spokesman, earlier told Iranian state television that 10 firehouses responded to the blaze, which was first reported around 8 a.m.
The Iranian military sent units to help with the disaster, state television reported.
Several embassies are located near the building. Turkey's state-run news agency, reporting from Tehran, said the Turkish Embassy located right across the street from the collapsed Plasco tower was evacuated as a precaution, though it sustained no damage in the collapse. Nearby British Embassy was also evacuated.
The Plasco building was an iconic presence on the Tehran skyline.
The 17-story tower was built in the early 1960s by Iranian Jewish businessman Habib Elghanian and named after his plastics manufacturing company. It was the tallest building in the city at the time of its construction.
Elghanian was tried on charges that included espionage and executed in the months after the 1979 Islamic Revolution that brought the current ruling system to power — a move that prompted many members of the country's longstanding Jewish community to flee.
The tower is attached to a multistory shopping mall featuring a sky-lit atrium and a series of turquoise-colored fountains. It wasn't immediately clear if the mall was damaged.