LAGOS  - The number of people killed in a building collapse in Nigeria’s economic hub, Lagos, has risen to four, an emergency management official said on Sunday. Five people have so far been rescued since the collapse of the building on a street in the Lagos Island area of the state on Saturday, Ibrahim Farinloye, coordinator of the National Emergency Management Agency in the southwest region, said in a statement. Cases of building collapses are not uncommon in Nigeria, and local experts blame them on aging structures, non-compliance with building planning and regulations, and the use of substandard materials during construction.