The school, which was on the top floor of the three-storey building in Ita Faji on Lagos Island, had more than 100 pupils.
Emergency officials, including men of the National Emergency Management Agency (NEMA), Lagos State Emergency Management Agency (LASEMA), and the police among others, had raced to the scene shortly after the incident for rescue operations.
TVCNEWS.TV has gotten reports from its correspondent, Theophilus Elamah who tells us that 12 persons have been confirmed dead while 42 injured are now receiving treatment.
It's gathered that over 100 students are now still trapped and being dug out. TVC Correspondent, Theophilus Elamah reports.
Dozens of children are feared dead after a building housing a primary school collapsed in southern Nigeria.
Also reacting to the incident, Lagos State Building Control Agency LASBCA, said the building that caved in had been marked for demolition since previous year because it was discovered by the Agency to be distressed.
"It's common to find schools in residential areas and in other locations that were not meant for educational institutions", Idris said. A resident of the area, who claimed he witnessed the collapse, said that rescue workers brought four pupils out of the rubbles dead.More news: WhatsApp and Instagram hit by outage
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People help a child after he was rescued from a collapsed building in Lagos, Nigeria.
Meanwhile, some residents of Itafaji area of Lagos Island reportedly pelted Governor Akinwunmi Ambode with sachets of water as he left the venue of the collapsed building.
Presidency Muhammadu Buhari said in a statement he was "extremely saddened" by the building collapse.
Building materials are often sub-standard and the enforcement of regulations in Nigeria is weak.
In December 2016, at least 60 people were killed by the collapse of a church roof in the city of Uyo, east of the country.
The same year, 30 people died when a five-storey building, under construction, collapsed in Lagos.