A building under construction in north-eastern Rwanda collapsed on Tuesday, killing at least three people and trapping others under the rubble, dpa reported. Police spokesman Theos Badege said 21 people were injured and rescue operations were under way in Nyagatare District, Eastern Province, about 100 kilometres north-east of the capital Kigali. "We are are unable to confirm details as to the cause of the building's collapse, but this will be subject to an urgent investigation that will begin as soon as the rescue operation concludes," Badege said in a statement.