Five people have been rescued and emergency workers have been digging through rubble to find survivors.
The site being built on Lagos Island is thought to have caved in during heavy rainfall.
An official said the building had been sealed off earlier because work violated safety regulations.
Oluwafemi Oke-Osanyintolu, head of the Lagos State Emergency Management Agency, said that despite the site being sealed off the developer continued to carry out work at night and on weekends.
The developer has not yet commented.
Nigeria building collapse
Building collapses are common in Nigeria and construction experts blame this on a widespread disregard for regulations.
Last November more than 40 people died when a partially-built block of luxury apartments crumbled in Lagos.