Lagos Health Commissioner Jide Idris told CNN on Friday those that were killed were mostly children from the school. Lagos State Governor Akinwunmi Ambode said earlier in the week that the school was operating illegally in the collapsed building.Forty-five people were rescued from the building and are now recovering at various government hospitals in the city, the health commissioner said."I'm delighted to note that the survivors of the unfortunate incident are calm, stable and responding to medical treatment and in no time, some of them who are certified and cleared will be discharged to join their families," Idris said.Rescue efforts ended on Thursday at the site in the densely-populated Ita-Faji area of Lagos Island, after officials said there were no more survivors.Building collapses are common in Nigeria's largest city with a population of around 20 million people. Angry parents and residents told CNN many of the buildings in the area were not safe. Read more: Boy, 6, dies and his twin sister is fighting for life after Lagos building collapseThe collapsed building had been marked for demolition at least three times, a buildings expert told the Nigerian News Agency. He said that there are many similar buildings in the Lagos Island area that are also at risk. "There are over 1,000 distressed other buildings of this nature in Lagos, which, if nothing is done to demolish them, they will still collapse, resulting to more calamities in the state," said Kunle Awobodu of the Building Collapse Prevention Guild. "The collapsed building had been marked for demolition about three times, but the building regulatory agency has not demolished it," Awobudu said. Governor Ambode, who visited the scene of the incident on Wednesday, confirmed that many homes in the area had structural problems and would be demolished.