Rescue work is ongoing at the site of a collapsed four- story residential building in Lagos, Nigeria. A police spokesman says at least 11 people have been killed and at least 21 people have been rescued from the rubble with injuries.  

Earth-moving equipment and rescue workers removed twisted metal and broken concrete blocks on Thursday in the hope of finding more people trapped under the residential building, which collapsed without warning on Tuesday.

"The rescue work is still ongoing. They are still searching through the rubbles to be sure there is no one in there. The casualty [count] remains unchanged," said Frank Mba, the Lagos police spokesman,

A Red Cross official at the site, John Adeyemo, blamed the slow pace of rescue efforts on what he called difficulties in coordinating all the groups involved.

"There is available equipment but they are not seen here at the right time. That is the main problem. You have Julius Berger [Construction Company] and other agencies that can easily help, but all these things would not be done at the right time. So we need to coordinate more. It is multi-sectoral. No government agency can do it alone. The Red Cross cannot do it alone," he said.

Nigeria has witnessed deadly house collapses in the past 20 years. Building experts have blamed the collapses on the use of sub-standard building materials and disregard for building regulations.

The Nigerian Institute for Building says 85 buildings have collapsed in the past 20 years in Nigeria, claiming more than 400 lives. This figure could be much higher as some of the collapses were not reported to the authorities.

In 2006, 28 people were killed when another four-story building fell down in Lagos.