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Two construction workers at the site in the affluent neighbourhood of Ikoyi, told Reuters that possibly 100 people were at work when the building came crashing down.

It was not immediately clear what caused the collapse but worker Eric Ntete said the labourers were “waiting for an excavator” at the time of the incident.

Eyewitness John Akpan said emergency workers did not arrive on site immediately.

The Lagos State Emergency Management Agency said it had activated its emergency response plan.

Building collapses are frequent in Nigeria, Africa's most populous country, where regulations are poorly enforced and construction materials are often substandard.