BRISBANE, Australia — Massive floods shut down the center of Australia's third-largest city, sent thousands fleeing from their homes and sparked panic buying of food on Wednesday as rescuers searched for 43 people missing in floodwaters.

At least 22 people have died in Australia's northeastern state of Queensland since drenching rains that began in November sent swollen rivers spilling over their banks, inundating an area larger than France and Germany combined.

The crisis escalated when a violent storm sent a 26-foot, fast-moving torrent — described as an "inland instant tusnami" — crashing through the city of Toowoomba and smaller towns to the west of Brisbane on Monday.