Lagos (AFP) - Thirty-four people died in the collapse of a five-storey building under construction in an upmarket area of Nigeria's biggest city, Lagos, a rescue official said on Wednesday.
"Operations concluded at 7:20 pm (1820 GMT) with 34 dead and 13 rescued alive after reaching ground zero," Ibrahim Farinloye, from the National Emergency Management Agency (NEMA), told AFP in a text message.
"Investigation on the cause of the collapse has started by various federal and state agencies," he added.
The fatal collapse happened after heavy rains in the early hours of Tuesday in the southeastern district of Lekki, which is home to some of the most expensive real estate in the city.
Lekki, made up of sprawling estates of gated communities with US-style suburban homes, has developed rapidly in recent years into a preferred location for wealthier Nigerians and expatriates.
Some detached houses can sell for millions of dollars.
Building collapses happen frequently in densely populated areas of Lagos, which is home to some 20 million people. Poor workmanship and materials, and a lack of official oversight are often blamed.
But collapses are rarer in wealthier districts.
The Lagos State government said in a statement that preliminary reports indicated work on the building was illegal but the order had been flouted.
- 'Brazen act of defiance' -
"The collapsed building was served (a) contravention notice for exceeding the approved floors" and was sealed by the Lagos State Building Control Agency, it added.
The owners of the building and promoters of the Lekki Gardens development, Lekki Worldwide Estate Limited, "criminally unsealed the property and continued building beyond the approved floors".
The government called the owners' actions "a brazen act of defiance and impunity" and said "integrity tests" should be conducted on all projects being handled by the company.
All work has been ordered to stop at the site and the owners told to report to the police within 24 hours or face arrest, Lagos State information commissioner Steve Ayorinde said.
"The State Government will no longer tolerate the action(s) of unscrupulous owners and builders who challenge its supervisory control thereby endangering the lives of Lagosians," he added.
"The State Government has consequently directed the suspension of work at the site and ordered the Lagos State Police Command to cordon it off as it is now a crime scene."
Lekki Gardens confirmed in a statement that construction had stopped in January "over reported structural defects" but made no mention of work having resumed.
It added: "Investigation is already under way to ascertain the identities of those affected as it is not company policy for site workers to take shelter in uncompleted buildings."
The addition of floors without proper planning approval was ruled to have been a factor in the collapse of a church guesthouse in Lagos in September 2014.
A total of 116 people were killed, 81 of them South Africans, in the collapse at the Synagogue Church of All Nations complex of popular evangelical preacher TB Joshua.
Joshua, church trustees and two engineers are currently on trial for criminal negligence and involuntary manslaughter.