Iranian officials said on Friday that 25 people were still unaccounted for after the collapse of a 17-storey commercial building in Tehran, in addition to 20 firefighters who were killed in the disaster, state TV reported.
Iranian media carried photos of weeping relatives and dozens of people lined up to donate blood and the government declared Saturday a day of national mourning.
"Police have received missing reports of 25 people. We urge people to report if any of their family members that worked in the Plasco building is missing," a police official told TV.
Thick smoke and fire were hampering the search for the bodies of at least 20 firefighters under the rubble more than a day after the blaze began.
Twenty firemen were killed as they evacuated people on Thursday from Iran's oldest high-rise building, built in 1962, which housed hundreds of clothing warehouses as well as a shopping mall and other businesses.
"Our aim is to recover the bodies of these martyrs without causing any damage to their bodies," head of Tehran's crisis management center Esmail Najjar told TV.
Fire department officials have warned of the danger of more explosions.
"We are trying any way possible to reach them ... but very thick rising smoke is making the work very difficult," Tehran's emergency services head, Pir Hossein Kolivand, told state TV.
"We are dealing with fire, thick smoke and lack of oxygen."
Iran's Supreme Leader Ayatollah Ali Khamenei visited one of the firefighters in hospital and President Hassan Rouhani has ordered an immediate investigation.
