Military helicopters searched Tuesday for scores of people missing after a tsunami-like wall of water ripped through an Australian valley, tossing cars like toys in the deadliest episode of a weekslong flood crisis. At least 10 people were killed and 78 still unaccounted for almost 24 hours after the flash flood hurled untold millions of gallons of water down Queensland state's Lockyer Valley on Monday, state Premier Anna Bligh said. Authorities had grave fears for at least 18 of the missing, she said. The valley funneled rain from a freak storm forecasters estimated up to 6 inches (150 millimeters) fell in half an hour near Toowoomba city into a stream that formed a path of destruction, lifting houses from foundations. The torrent slowed and spread out as it moved downstream toward the state capital of Brisbane, Australia's third-largest city with some 2 million people. The Brisbane River overflowed its banks Tuesday and officials warned that thousands of houses in dozens of low-lying neighborhoods and parts of downtown could be inundated by Thursday. Residents queued for up to four hours outside emergency services depots on Tuesday to get sandbags to try to protect their homes, and shoppers stocked up on bottled water, milk and fuel. Residents in at least three suburbs were asked to prepare their homes, then go and stay with friends or family on higher ground.