At least 16 people were killed and nearly three dozen injured Sunday when a four-story building collapsed onto a smaller one in Cameroon's largest city, authorities said.

"The casualty figures may be higher, said Samuel Dieudonne Ivaha Diboua, governor of Cameroon's Littoral region, where the Douala is located. The city is west of the capital, Yaounde.

The governor said that "rescue workers, assisted by Cameroon government troops, are still digging the wreckage to see if more bodies can be recovered."

The military's fire brigade has been ordered to join the country's Red Cross and other rescue services in searching for survivors.

Residents living in the Ndogbon neighborhood where the incident took place said they are in shock.

"We heard people screaming … and struggled to help some out of the wreckage, but could not do it with our spades and (garden) hoes," said Gaspard Ndoppo, who lives near the collapsed buildings.

Building collapses happen often in Douala, sometimes due to natural disasters such as landslides and other times because of poor construction, locals say.

Douala's city council is currently demolishing houses in high-risk zones susceptible to floods or landslides. The building that collapsed on Sunday was not marked for demolition.