A five-story apartment building collapsed early Wednesday, killing at least one and injuring 26 others, the governor said.
Officials blamed the collapse on shoddy construction but could not provide an immediate explanation. It was not clear how many people were inside when the building came down after midnight. Istanbul Gov. Muammer Guler said at least 27 people were living in the destroyed building.
A municipality worker and the owner of a coffee shop, in the basement of the building, alerted the residents by ringing the bells, shouting and throwing pebbles at the windows and saving many lives, authorities said.
"We think maybe just a few more people remain buried," under the destroyed building, Guler said.
Guler earlier said rescuers reported that a seven-year-old girl was pulled out dead but when she was taken to hospital, doctors said she was alive though barely breathing. Her face was covered in a white film of dust that was mostly crushed concrete when she was pulled out.
"She is alive and connected to a respiration machine," Guler said. The state-run Anatolia news agency identified the girl as Evin Demir, adding that she was in critical condition.
Guler said 26 people were hospitalized, including some who escaped from the coffee house.
There was no credible information about why the building collapsed but media reports suggested that its foundations might have been weakened by an adjacent construction. Istanbul Mayor Kadir Topbas confirmed that the building was listed as unsafe and one needed to be pulled down against a quake.
Ali Karahan, chief of Istanbul firefighter department, said some residents managed to escape the building when it began crumbling and those who were injured were all trapped in the stairway.
A municipality worker who was walking in the street by chance saw the building rocking and alerted the residents by shouting and throwing stones at the windows, Topbas said.
Ilhan Karadeniz, the owner of the coffee shop, said he woke up his neighbors when he noticed that the building was shaking.
"I was doing cleaning when I heard columns crumbling, I quickly rushed out and began ringing the bells," private Dogan news agency quoted Karadeniz as saying.
Idris Gunes, an injured survivor, left the building upon hearing the warnings.
"When we heard them, we rushed out," said Idris Gunes, a survivor told private NTV television. "Everybody was in a panic and trying to help each other," she said. "But some people could not leave in time."
Teams, helped by sniffer dogs, were still working under floodlights to find out whether any other people were trapped under the rubble of the building in residential Zeytinburnu district. Rescuers were pulling away pieces of concrete with their bare hands and with the help of excavators, the AP reports.
Turkish rescuers often carry out earthquake drills in Istanbul to test the earthquake preparedness of this sprawling city of more than 12 million that experts believe could be hit by a huge temblor sometime in the next 30 years.
Geologists have urged the Turkish government since 1999 - when two earthquakes west of Istanbul killed more than 18,000 people - to tear down some 50,000 buildings that would probably collapse if a big quake hits Istanbul.
They say hundreds of thousands of other buildings that rise in an unstable mass of brick, mortar and stone, need to be reinforced, the AP reports.
Topbas said the collapsed building was on the list of 16,000 other buildings marked as unsafe and needed to be pulled down in Zeytinburnu district alone.
Shoddy construction was also blamed for many of the deaths in two 1999 quakes in western Turkey. Experts say little has been done to address the problem of poor construction.
Several contractors who were charged with negligence for ignoring building codes escaped punishment this week when statute-of-limitations expired in all ongoing cases that were filed in 1999.