A two-story school collapsed during morning classes Friday in north-central Nigeria, killing 22 students and sending rescuers on a frantic search for more than 100 people trapped in the rubble, authorities said.

The Saints Academy College in Plateau state’s Busa Buji community collapsed shortly after students, many of whom were 15 years old or younger, arrived for classes.

A total of 154 students were initially trapped in the rubble, but Plateau police spokesperson Alfred Alabo later said 132 of them had been rescued and were being treated for injuries in various hospitals. He said 22 students died. An earlier report by local media had said at least 12 people were killed.

Dozens of villagers gathered near the school, some weeping and others offering to help, as excavators combed through the debris from the part of the building that had caved in.

One woman was seen wailing and attempting to go closer to the rubble as others held her back.

Nigeria’s National Emergency Management Agency said rescue and health workers as well as security forces had been deployed at the scene immediately after the collapse, launching a search for the trapped students.

“To ensure prompt medical attention, the government has instructed hospitals to prioritize treatment without documentation or payment,” Plateau state's commissioner for information, Musa Ashoms, said in a statement.

The state government blamed the tragedy on the school’s “weak structure and location near a riverbank." It urged schools facing similar issues to shut down.

Building collapses are becoming common in Nigeria, Africa’s most populous country with more than a dozen such incidents recorded in the last two years. Authorities often blame such disasters on a failure to enforce building safety regulations and on poor maintenance.