Map locating Nyagatare in Rwanda
Authorities were searching for survivors on Wednesday after the building collapsed late on Tuesday afternoon in the eastern Rwanda district of Nyagatare, in what police called an "unfolding tragedy".
At least 30 workers injured in the collapse are now being treated at a nearby hospital, said Christophe Semuhungu, the police spokesperson for Rwanda's Eastern province.
It was yet clear what caused the collapse or even how many people are feared buried under the rubble.
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.
The building in Rwanda collapsed some 100km north-east of the capital Kigali and rescuers were scrambling to find survivors, police said on Tuesday.
"We think between 30 to 50 people were working on the building when it collapsed. We are continuing our rescue operations now," police spokesperson Theos Badege said at the time.
The cause of the collapse
A further 21 were injured and were being treated in hospital, police said in a statement on Tuesday.
The Rwanda Defence Forces and the police had secured the site and were coordinating the rescue operation, police added.
The town is the largest in the north-eastern region, sandwiched between Rwanda's border with Uganda and Tanzania near the Akagera National Park.
Police on Tuesday said they were unable to establish the cause of the building's collapse, but this would be subject to an investigation by local and national authorities once the rescue operations were concluded. – Sapa-AP; additional reporting by Reuters