Search efforts were called off at the site of a school building that collapsed in the Nigerian city of Lagos, as rescuers were trying to find a register of children to work out how many have died.

Workers have reached the foundation of the collapsed three-storey building and don't expect to see any more bodies, Ibrahim Farinloye, a National Emergency Management Agency official, told The Associated Press on Thursday.

He declined to give an updated toll of the dead and the rescued.

Officials said late Wednesday that eight people had died and 37 had been pulled out alive. An unknown number remain missing.

Residents said some 100 children had attended the nursery and primary school, and people were searching through the tangle of rubble and metal on Thursday to find any belongings of their loved ones.

A few hundred people watched from nearby as an excavator dug through the remains of the debris.

At the site of the collapse, people searched through the tangle of rubble and metal Thursday to find any belongings of their loved ones. By the afternoon, most of the debris had been cleared away.

"We have been able to pull down the remaining part of the building," said Adebayo Kayende, spokesperson for the Lagos state emergency agency.

Rescue workers help carry a child at the site of the collapse Wednesday. (Afolabi Sotunde/Reuters)

"We have moved the debris from the ground to have a clear picture to make sure there are no people under the building."

Kayende said the Lagos state ministry of health was checking with hospitals, and once they had finished counting those dead the details would be made public.

Full investigation

Adesina Tiamiyu, general manager of the Lagos state emergency agency, said the number of children involved was still in question and authorities were trying to find a register of the pupils.

Lagos Gov. Akinwuni Ambode, who visited the site hours after the building collapsed, said the building, which had been marked for demolition, was classified as residential and the school was operating illegally on the top two floors. There will be a full investigation into the incident, he said.

Officials moved through the neighbourhood on Thursday, marking other derelict buildings for demolition.

Obiora Manafa with the Standards Organization of Nigeria told reporters that they would analyze samples of the collapsed building's concrete and steel bars "to ascertain the quality ... and know whether they complied with the national building code."

"It touches one to lose precious lives in any kind of mishap, particularly those so young and tender," Nigerian President Muhammadu Buhari said.