“So far, the tentative information we have indicates that debris fell on about 100 people, we are yet to come up with the exact figures,” Rwandan Minister of Disaster Management Seraphine Mukantabana told AFP.
Police spokesman Theos Badege said that three people were confirmed dead and 21 people had been taken to hospital.
Those trapped are believed to include both construction workers on the building as well as passersby on the street.
The building, on a roadside in the town of Nyagatare, some 100 kilometres (60 miles) northeast of the capital Kigali, collapsed on Tuesday afternoon.
“At the moment we are working with the police on a quick response,” Mukantabana added.
“The building that collapsed was a four- storey located in Nyagatare district by the roadside, and that is why it affected many people.”