Brazil has declared three days of national mourning for at least 610 people killed near Rio de Janeiro this week in the country's worst flood disaster on record. Emergency workers in the disaster zone, in the Serrana region just north of Rio, were overwhelmed by the body count, with refrigerator trucks brought in to store corpses. Workers transporting bodies said they feared the overall death toll could rise 1,000 as rescuers reached outlying hamlets.While President Dilma Rousseff declared the three days of mourning, Rio de Janeiro state authorities said their state will observe a full week of mourning starting tomorrow.