At least 30 firefighters are reported to have been killed when a burning building in the capital of Iran collapsed.
Another 75 people were injured when the disaster struck the Plasco building in central Tehran, just north of the capital's bazaar, state media reported.
Firefighters, soldiers and other emergency responders dug through the rubble, looking for survivors.
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 most intense in the building's upper floors before the collapse. Those floors were home to garment workshops.
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 of the injured and take immediate action to compensate 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.
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," she 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 fire houses responded to the blaze, which was first reported around 8am.
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 was evacuated as a precaution, though it sustained no damage in the collapse.
The 17-storey Plasco building 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.