The state commissioner for Physical Planning and Urban Development said no fatalities were confirmed, adding that those who sustained injuries were receiving treatment.
"From the preliminary report and [an] eyewitness, it was a seven-story building that collapsed due to the fact that a truck ran into the building," Dr. Olufemi Oke-Osanyintolu, permanent secretary for Lagos State Emergency, Management Agency, or LASEMA, said.
"We have seven casualties; all the people that were involved has been treated and discharged except one that was transferred to a private hospital that is nearby for a proper medical treatment."
Oke-Osanyintolu said the area has been cordoned off, and an investigation is under way.
Media reports say the accident occurred as construction workers on the sixth floor of the building were attempting to build the seventh floor. Two adjacent nine-story buildings also under construction have not been affected.
According to the Peoples Gazette website, Rotimi Edu, the president of National Emergency Management Agency, said "the collapse brings [into question] the continuous recalcitrance of building contractors to adhere to extant regulatory prescriptions concerning public buildings in the country."
Lagos State Commissioner for Physical Planning and Urban Development, Tayo Bamgbose-Martins, told Radio Nigeria that the government did not grant approval for the construction.
Documents from the Building Collapse Prevention Guild in Lagos state said 155 buildings have collapsed in the past 10 years – including 20 last year.