Twenty-one people died after a school building collapsed in central Nigeria while students were sitting an exam in what local authorities called an “avoidable tragedy.”

The two-story building collapsed in the city of Jos and saw a further 30 people hospitalized, according to Nigeria’s National Emergency Management Agency (NEMA).

NEMA said that students were amongst those who died in Jos, the capital of Plateau State, without providing an exact number.

Around 120 people were trapped when the building collapsed, according to Plateau State government.

The governor of Plateau State, Caleb Manasseh Mutfwang, said the building collapsed as students were sitting an exam. Mutfwang expressed his “deep sympathy to the families of students and staff of St. Academy School.”

The Plateau State government said in a statement Friday: “The government describes the incident as an avoidable tragedy, citing the school’s weak structure and unsafe location near a riverbank.”

Local hospitals have been instructed by the government to provide treatment without documentation or payment.

Schools with similar safety issues have been urged to close down, the government said.

Building collapses are common in Nigeria due to lax construction standards and poor quality materials.

This post appeared first on cnn.com