BRISBANE, Australia - Australian police  have launched a major search and rescue operation after devastating flash floods killed eight people, left more than 70 missing and threatened on Tuesday to swamp the country's third-largest city.

A flash flood sweeps vehicles down a street in Toowoomba, 105 km (65 miles) west of Brisbane Jan 10, 2011. [Photo/Agencies]

The death toll from the worst flooding in the state of  Queensland in half a century was expected to climb, state  premier Anna Bligh told journalists, saying the situation was  grim and desperate.

Four were killed in Toowoomba, a town west of Queensland state capital Brisbane, after heavy rains sent a 2-metre wall of water through streets on Monday, carrying away cars and  pedestrians.

"It just picked up cars like matchbox toys," Toowoomba  resident Debbie Huxley told Sky TV. "You would never have  believed it unless you saw it."

TV footage showed brown floodwater gushing through the centre of Toowoomba laden with debris, as people clung to  telephone poles and rooftops to survive. There are growing  fears the floods could soon hit Brisbane, a city of 2 million  people. 

"This is going to be I think a very grim day, particularly  for the people in that region, and a desperate hour here in  Queensland," Bligh said on Tuesday.

"Right now we have every possible available resource  deployed into this region to search for those people that we  know are missing," she said.

Two women and a child were killed at Grantham, a township  between Toowoomba and Brisbane. Nearby at Withcott, police  said nine people were missing and the death toll was likely to  rise.

"It's like an atomic bomb hit this place," Steve Jones, mayor of Lockyer, another town affected by the downpour, told  the Courier Mail newspaper. "The intensity was impossible to explain."

Rivers in some areas rose more than 8 metres in an hour, catching residents and authorities completely by surprise.

Police said more than 40 people were plucked from rooftops by helicopter overnight, while helicopters and military  personnel were due to begin searching for more than 70 people  reported as missing in the Locker River valley.

Damage caused by floods in Queensland that started after  heavy rains before Christmas could reach $6 billion,  economists say, after destroying homes, roads and rail lines,  as well a paralysing the state's key coal mining sector.

"I personally believe it will get worse today," Queensland  Disaster Coordinator Deputy Commissioner Ian Stewart told  Australian television.

Blight said a major incident room had been set up in  Brisbane to coordinate a rescue operation.

 Worst Queensland floods in 50 years

The worst floods in the state in 50 years have at times  covered an area the size of France and Germany combined. At  least 12 people have been killed, while dozens of towns have  been isolated or partly submerged, with more rains expected.

Flooding was expected to reach Brisbane, where hundreds of homes and businesses in 32 suburbs along the swollen Brisbane  River and further west were under threat.

Authorities have made sandbags available for residents after some experts described conditions as similar to those  when the city was hit by deadly floods in 1974.

The floods have also paralysed operations that produce 35 percent of Australia's estimated 259 million tonnes of  exportable coal. Australia contributes two-thirds of world  exports of steelmaking raw material coking coal.

Coal seam gas drilling in the Surat Basin, a big source of  gas for an estimated $200 billion in proposed liquefied  natural gas projects, was halted on Monday by flooding.

Global miners Anglo American, Rio Tinto, Xstrata and BHP Billiton, have been hit by the floods, and all have made force majeure   declarations, which release firms from delivery commitments.

Flooding has begun to recede in the main Bowen Basin coal region, but many mines remain flooded and will take weeks to   drain and resume full production. While some rail links  between mines and the ports have been opened, others are under  water.  

Coal stocks were running low at the key coal port of Dalrymple Bay, but it was receiving enough to keep loading  ships, while the port of Gladstone said it could be days to weeks before it starts getting coal supplies back to normal.