KAMPALA, Uganda (AP) — Six people were killed and dozens more injured when a four-story building under construction collapsed in eastern Rwanda, police said Wednesday as the rescue effort ended. Christophe Semuhungu, the police spokesman for Rwanda's Eastern Province, said rescue workers from the police and the military had found no more bodies after combing through the rubble of the building in the eastern Rwanda district of Nyagatare. He said at least 30 workers were injured in the Tuesday afternoon incident. Most were being treated for minor injuries at a nearby hospital, he said, but some were in critical condition. He said the construction site employed about 45 workers but some were not on duty when the building fell. In a statement police had earlier described the building collapse as "an unfolding tragedy." It remained unclear what caused the collapse. In recent years building collapses have become frequent in East and Central African countries as some property developers bypass regulations to cut costs. In March, a building collapsed in the Tanzanian city of Dar es Salaam, killing at least 30 people.