JOS, Nigeria — A school in central Nigeria collapsed on Friday killing at least 21 people, mostly pupils as they were sitting their exams, the Red Cross and witnesses said.

Trapped pupils cried for help under the rubble as desperate parents looked for their children after the Saint Academy school in Jos North district of Plateau State fell in on classrooms, according to an Agence France-Presse correspondent at the scene.

Rescue workers tried to reach the victims with heavy machinery and images from the scene showed crowds gathering around a caved-in concrete building and heaps of debris.

Red Cross spokesman Nuruddeen Hussain Magaji told AFP there were "21 fatalities, and 69 injuries all in admission at various hospitals."

Earlier, AFP saw 16 bodies in two hospital morgues in Jos. All were wearing school uniforms.

With his mother at his hospital bedside, injured pupil Wulliya Ibrahim, 15, told AFP: "I entered the class not more than five minutes, when I heard a sound, and the next thing is I found myself here."

"We are many in the class, we are writing our exams," he said.

Earlier, the National Emergency Management Agency said the two-storey building housing Saint Academy collapsed killing "several students."

Chika Obioha, a resident at the scene, told AFP he saw at least eight bodies at the site and that dozens more had been injured.

"Everyone is helping out to see if we can rescue more people," he said.

AFP's correspondent said he saw 11 bodies in the morgue at the Bingham University Teaching Hospital and that five dead were taken into the mortuary at the Our Lady of Apostles Hospital in Jos.

At least 15 rescued and injured pupils were admitted, officials at the Our Lady of Apostles Hospital said.

Officials at the Bingham University Teaching Hospital did not comment.

It was not immediately clear what caused the collapse but residents said it came after three days of heavy rains.

"Devastated by the tragic loss of young lives at Saint Academy," UNICEF Nigeria representative Cristian Munduate wrote on X.

"Children, full of dreams were writing exams when the school building collapsed. Deepest condolences to families affected."

Building disasters are fairly common in Africa's most populous nation because of lax enforcement of construction standards, negligence and low-quality materials.

At least 45 people were killed in 2021 when a high-rise building under construction collapsed in the upscale Ikoyi district in Nigeria's economic capital Lagos.

Ten people were killed when a three-storey building collapsed in the Ebute-Metta area of Lagos the year after.

Since 2005, at least 152 buildings have collapsed in Lagos, according to a South African university researcher investigating construction disasters.

Bad workmanship, low-grade materials and corruption to bypass official oversight are often blamed.