Thousands of people prepared to flee floods in Australia's north-east Thursday as rising waters swamped towns, roads and railways in an 'unprecedented' multi- billion-dollar disaster. As hundreds of displaced residents sheltered in evacuation centres and towns battened down for some of the worst deluges on record, Queensland state premier Anna Bligh warned the crisis could drag on for days or weeks. 'This is a disaster on an unprecedented scale,' Bligh told reporters. 'This is a massive disaster and many, many people are doing it very tough, (they're) out of their homes and may not be returning for some time.' Tropical cyclone Tasha caused widespread flooding over Christmas in the economically important farming and coal-mining area near Brisbane, and rivers are still rising as rainwater flows downstream. Floods were expected to hit 80 percent of the rural town of Emerald after a nearby river passed record levels, while the sugar-cane centre of Bundaberg -- known for its famous rum -- was split in two by the inundation. Elsewhere in the state, police feared the monsoonal downpour had claimed its first life after the body of a 50-year-old man, believed drowned, was fished out of a swollen river near Cairns. Military helicopters have already helped to evacuate more than 1,000 residents after about a dozen rural settlements were cut off. But hundreds more homes in various towns remain at risk as river levels continue to rise. Bligh said the damage bill would run into several billions of dollars (several billion US) but warned that the disaster's true extent would not be known until the floods subside, up to 10 days from now. 'We've got a long way to go ahead of us and when these waters recede, that is when we're really going to know the size of the problem,' she told reporters. 'That is when many people will get back into their homes and it will really hit them just how many of their precious family possessions have been washed away forever,' she added. Global miner Rio Tinto declared 'force majeure' at four coal mines, meaning that production may be affected, while vast swathes of cotton and sugar-cane farmland have disappeared under the muddy waters. Large parts of the state have been declared natural disaster areas, giving them access to emergency funds, while Brisbane's Courier-Mail said the damage could send prices of melons, tomatoes, mangoes and bananas soaring. Queensland Shark Control Program manager Tony Ham also told the newspaper that floods could have flushed bull sharks out of major rivers and into popular swimming and surfing spots. Similar warnings have been made about crocodiles. The floods have caused serious damage to infrastructure, swamping rail lines and washing away roads, while Rockhampton's airport was under threat of closure. Meanwhile weather forecasters warned that another cyclone was forming off Western Australia, on the other side of the huge country, while extreme heat posed a wildfire risk in South Australia. 