Thousands of people gathered in the area sa the authorities began rescue efforts. A local resident told the AFP news agency that at least 10 people were still trapped inside the building, which also housed a nursery and primary school on the top floor.
A police officer said at least 20 people had been dragged from the rubble, not specifying whether they were dead or alive.
The incident is reported to have taken place at around 10:00am local time. Victims were pulled from the wreckage covered in dust, some with blood on their faces.
Associated Press said that as many as 100 children could have been attending the nursery and school at the time. It was not immediately clear how many had registered for classes on Wednesday.
Local television reports depicted residents assisting rescue efforts with spades in their hands, clearing the debris. Rescue workers had deployed an excavator and were clearing large slabs of concrete.
An eyewitness speaking to The Punch newspaper said the building had twice been earmarked for demolition, casting doubt on the building’s structural integrity.
Building collapses are common in Nigeria with building regulations regularly ignored.
At least 60 people were killed in December 2016 when a church roof collapsed in Uyo, in Akwa Ibom state. More than 110 people died in September 2016 when a six-storey building collapsed during a church service.