it s unclear why the structure suddenly caved in. it isa it is a race against time. rescue workers crawl through rubble in search of people trapped under a building which housed a hotel, apartments and cinema. the multi story structure in a densely built street caved in on friday leaving a gaping hole. 700 firefighters and large evacuation diggers have been deployed, along with life detectors and rescue dogs. at a press conference, the mayor of changsha said that teams are working around the clock. irate changsha said that teams are working around the clock. around the clock. we will make every effort to search around the clock. we will make every effort to search for around the clock. we will make every effort to search for those around the clock. we will make every effort to search for those still - effort to search for those still trapped on the principle of life first, people first. we have a 72 hour window and we will try our best to rescue those still missing. maw;