ABUJA, Nigeria (AP) — Nigerian rescue officials say they are working to pull out a number of people trapped under the rubble of a collapsed shopping complex that was under construction in the capital, Abuja.

Labaran Ahman, Federal Capital Emergency Agency search and rescue chief, said Friday that many people were rescued by bystanders after the four-story building collapsed in the afternoon. He said the number of people trapped is unknown.

Abass Idris, a Nigerian Emergency Management Agency official, said the building had been abandoned and new construction restarted recently. He said the owner may have altered its original plans in that time, affecting the stability of the structure.

Building collapses are not uncommon in Nigeria, a West African powerhouse where corruption is rampant and infrastructure is often poor.