Lagos, Nigeria — Rescue efforts were underway in Nigeria on Wednesday after a three-story building housing a school collapsed while classes were in session. About 100 children were thought to be inside at the time of the collapse, but there were conflicting reports about how many might be missing in the rubble.

Lagos provincial governor Akinwunmi Ambode was quoted by the Reuters news agency as saying 25 people had been pulled out of the debris, "some already dead."

Ibrahim Farinloye, a spokesman for Nigeria's National Emergency Management Agency, told CBS News partner network BBC News earlier Wednesday that the building came down around 10 a.m. local time, and "it is believed that many people including children are currently trapped."

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Associated Press video from the scene showed at least one dust-covered child being carried out of the crumbled concrete. Onlookers crowded around the area in the densely populated neighborhood in Lagos, Nigeria's commercial capital. They cheered as the child was lifted out. Hundreds of people stood in narrow streets and on rooftops of rusted, corrugated metal. A yellow excavator scooped at the ruins.

Rescue workers are seen at the site of a collapsed building containing a school in Nigeria's commercial capital of Lagos, Nigeria, on March 13, 2019. Reuters

Sani Datti, a spokesman with Nigeria's National Emergency Management Agency, told The Associated Press that officials from the agency and other emergency services were at the site.

"For now we don't have any word on casualties as we are still busy with rescue work," he said.

Building collapses are common in Nigeria, where new construction often goes up without regulatory oversight. The school was on the third floor of the building that collapsed.