Baton Rouge - The death toll from historic flooding in the US state of Louisiana went up to eight on Tuesday, as the expanding flood zone prompted authorities to declare disasters in a dozen parishes.While waters were receding in parts of southern Louisiana, other areas were seeing rising waters. The National Weather Service issued renewed flood warnings."We're seeing unprecedented flood levels as the waters move south," Louisiana Governor John Bel Edwards said at a news conference.Officials said 40 000 homes have been impacted by the floods, and more than 8 000 people were in shelters.More than 20 000 have been rescued or evacuated, they said.A dozen parishes - similar to counties in other states - have now been declared emergency disaster areas, up from four on Monday.The designation frees up federal money to aid with rescue operations and emergency housing, among other things."There are still a lot of people who are suffering," including the 34 000 customers who remain without electricity in summer heat and humidity - raising concerns of mould, the governor said.Rescue crews were searching flooded homes and cars for more victims, with officials uncertain how many people remain missing."We are going door to door," said Baton Rouge Fire Department Chief Ed Smith, describing a search and rescue process that he said could take another five to seven days.The National Weather Service issued 29 new flood warnings on Tuesday for parts of southern Louisiana, as the levels of certain waterways continued to climb.The governor had initially asked the federal government to declare disasters in 21 parishes, and he said more parts of southern Louisiana could still get that designation.