Authorities in Nigeria say 20 people are confirmed dead in the school building that collapsed on Wednesday, and most of them are children.

Lagos State Health Commissioner Jide Idris tells The Associated Press that 43 other people were rescued alive.

Officials have said the three-story residential building had been marked for demolition and that the school was operating illegally on the top two floors.

Rescue crews halted their search on Thursday, to the anger of some at the scene, saying they had reached the building's foundation without finding any other victims.

Building collapses are all too common in the West African nation, where new construction often goes up without regulatory oversight.