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By Luis Manuel Lopez

VILLAHERMOSA, Mexico, Oct 31 (Reuters) - Around half a million Mexicans were made homeless and one man died on Wednesday as heavy rains devastated the southern Mexican state of Tabasco and flooded 70 percent of the swampy region.

Television images showed many towns and much of the state capital Villahermosa turned into huge brown lakes with only the tree tops visible above the waterline as floodwaters poured over sand-bagged riverbanks and destroyed crops.

The floods, caused by a cold front that has wreaked havoc with the oil industry along Mexico's Gulf coast, were the worst in the state's history, said Gov. Andres Granier.

"The amount of water is incredible. We have lost 100 percent of our crops and 70 percent of the state is under water," Granier told reporters.

The state government said about half a million people were made homeless as the floods destroyed tens of thousands of homes.

Floodwaters half-covered several giant carved stone heads built by the Olmecs, America's first great civilization, at the state's La Venta archeological site. Some of the heads are over 9 feet (3 metres) tall.

Mexican President Felipe Calderon flew to the low-lying, banana- and oil-producing state on the country's tropical Gulf coast to assess the damage and promised aid and more soldiers and rescue workers.

Soldiers and naval officers desperately loaded sandbags along city streets in Villahermosa to stop the floodwaters from spreading. Helicopters rescued stranded residents from rooftops.

Many residents waded through the waters to get to higher ground and some carried pieces of furniture as they tried to save their belongings.

Some 20,000 people were moved to shelters but a lack of tents meant many others were forced to sleep in parks.

The state government said one man died in the floods, but did not give more details.

Bad weather from the cold front caused an oil platform to collide with another rig last week, killing at least 21 workers. Stormy seas closed Mexico's three main oil ports on Sunday, halting almost all exports and a fifth of production. Two of the ports were operating again on Wednesday.

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