About 88 people, including firefighters, were also injured when the Plasco building caught fire and collapsed.
Iranian officials said on Friday that 25 people were still unaccounted for in the collapse of a 17-storey commercial building in Tehran on Thursday, Iran's state TV reported.
Twenty firemen were killed as they evacuated people 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.
"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 the broadcaster.
About 88 people, including firefighters, were injured when the Plasco building caught fire and collapsed. Only three were still in hospital, state TV reported.
"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 said.
Iran's Supreme Leader Ayatollah Ali Khamenei visited one of the firefighters in hospital and President Hassan Rouhani has ordered an immediate investigation.
The building's managers had ignored repeated warnings about poor safety standards and the building's weak structure, Tehran's mayor Mohammad Baqer Qalibaf said on Thursday.