beijing least three people killed others trapped debris building collapsed imputable suspected gas leak office southwest china blast occurred office wulong district chongqing municipality trapping people pulled detritus three died rescue efforts quoted emergency brake response team up accident took place pm local clock due suspected gas leakage triggered explosion caused collapse mobile canteen building municipal publicity section look others buried debris xinhua news agency witnesses people dejeuner canteen blast took place number people injured rushed hospital rescue work underway xinhua ministry pinch management dispatched several experts guide rescue hand brake management huang ming called efforts immediately inspect site find precise number victims trapped determine cause accident forestall mishaps happening firefighters professional rescuers well grouping rescue dogs racing time search trapped recent months witnessed explosions restaurants killing injuring many people largely blamed gas leak