At least 75 people, including 45 firefighters, were injured when a blazing high-rise commercial building in downtown Tehran collapsed, Iranian state television reported on Thursday.
One witness described the 17-storey tower's collapse as like a "scene from a horror movie".
Meanwhile, other Iranian media reports suggested that over 30 firefighters had been trapped and were feared dead.
Rescue teams were at the scene, state TV said.
Everyone else had been evacuated from the building, state TV said, but firefighters were still trying to control the blaze and police have cordoned off the area.
"The building is one of the oldest buildings in Tehran. The Plasco building is a very old building in southern Tehran. It is mostly a commercial building," state TV said, referring to the Plasco Building, which is more than 50 years old.
"At least 45 firefighters are among the injured ones. All of the injured people were sent to hospitals. Most of them have been discharged," state TV reported.
The semi-official Tasnim news agency said the Plasco building "had caught fire in the past".
"The fire started on the ninth floor ... The fire is almost under the control now," Tasnim reported.
A grocery shop owner, forced by police to leave the area, told Reuters by telephone that "it was like a horror movie. The building collapsed in front of me."
The semi-official Fars news agency said police have cordoned off British and Turkish embassies that are located near the Plasco building.
"The flames could be seen kilometers away from the old building ... but most of the residents and shopkeepers in the building have been evacuated," the semi-official Fars news agency reported.
"The fire started around 8 a.m. (0430 GMT) local time when many shopkeepers were not inside the building," it said.