Mass evacuations were under way in northern Australia on Sunday as record flooding that has cut off thousands of people threatened to engulf areas devastated by wild weather last year. Authorities urged residents of St George, a town of 3,800 people in the state of Queensland, to leave their homes as rising floodwaters threatened to isolate the area, with time running out to shore up a levee. "Whilst the extent of potential flooding in St George is still not certain, the volume of water approaching the town in the next 24 to 48 hours is significant, and the advice to evacuate is undertaken in the interest of public safety," said state Premier Anna Bligh. "Those who have vehicles are asked to leave as soon as possible and go to family and friends in other towns not affected by flooding." Buses were being arranged to an emergency refuge in nearby Dalby for those without other options, and Bligh warned that forcible evacuations were possible within 24 hours. "A decision on this issue is expected later this afternoon," she said. Prime Minister Julia Gillard dispatched a Hercules C130 military transport plane to airlift patients from the town's hospital to major medical facilities on the coast, and the local nursing home was also being emptied. Eight defence helicopters are already assisting search, rescue and resupply operations in the flood zone, winching people to safety and dropping food, bedding, medical supplies and other essentials such as generators. St George has seen major flooding twice in the past two years, with the swollen Balonne River hitting a record 13.4 metres (44 feet) in March 2010. The town was swamped again during last year's unprecedented flooding, which claimed 35 lives across the state, wrecked vast tracts of farmland and inundated tens of thousands of homes. Deputy Queensland police commissioner Ian Stewart said the situation in the region had "somewhat deteriorated" overnight with "very large spikes" in water levels south of Roma, where 200 homes flooded earlier this week. "We are working on our contingencies to manage the evacuation of areas south of Roma and in particular St George," Stewart said. "There are very large volumes of water in those systems getting to record levels." Stewart said there was still time for residents to flee but forced evacuations were being "very seriously" considered to ensure resident safety. The Bureau of Meteorology said St George was expected to reach the 2010 flood level by Monday morning and "continue rising, possibly above 14 metres on Tuesday and Wednesday." Residents scrambled to fortify levees still standing from last year's floods, with some locals saying they were prepared for a peak of 14.5 metres or worse. "If it does reach the peak that they're talking about, if it goes across into the irrigation area, it's going to knock out thousands of hectares of cotton," local farmer Alex Benn told Sky News. "We're a bit concerned so we're topping all the levees up." Flood defences held overnight in nearby Charleville, where some 600 people were holed up in an evacuation centre waiting for the Warrego River to subside. Waters were slowly easing in Roma, where a woman whose car was swept off a road on Friday remained missing.