A shopping mall roof collapsed Thursday night in Riga, Latvia, killing 51 people as of Friday evening. The collapse took place at about 5:45 p.m., when the residential mall in the capital city was packed with after-work shoppers. Rescue efforts are ongoing and the mayor of Riga, Nils Usakovs, tweeted that around five people may still be trapped. "We're still having moments of silence to listen for voices of people trapped, but unfortunately the only voices out there are of firefighters working," said a state police spokesman. At least three of the casualties were firefighters who had responded to the scene and were caught in a secondary collapse. News reports said a garden was being constructed on the roof of the mall, and soil from the project might have triggered the first collapse.