The view into Brazil from this Bolivian border city seems like an Amazon jungle paradise: an endless green horizon broken only by the modern skyline of the Brazilian city of Corumba shimmering in the Caceres Lagoon. But authorities say the largely unguarded tangle swamps, rivers and jungles hide an increasingly sophisticated cocaine trade.

Controlling the 2,130-mile frontier has been a low priority for Brazil and Bolivia, which have been preoccupied by tense negotiations over the Bolivian gas Brazil buys.

Bolivia has just 157 border officers — one for every 105 miles. On the Brazilian side, some 100 border posts are manned by a patchwork of local and national officers. Chemicals used to turn Bolivian coca into cocaine flow easily from Brazil, and processed coca paste slips just as easily back over the border, officials say.

"We have noticed a growth in the traffic of cocaine, and principally cocaine paste, over the last two years," Marcio Paulo Buzanelli, director of the Brazilian Intelligence Agency, told The Associated Press. "One indication of this are the seizures in the Brazilian states that border Bolivia."

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Cocaine seizures climbed by 14 percent last year to 3,461 pounds in Brazil's Mato Grosso do Sul state, and leaped nearly 347 percent to 1,477 pounds in Rondonia state.

The busts pale in comparison to seizures along more heavily traveled smuggling routes father north in the Caribbean, and Bolivia remains a distant third among cocaine producing nations behind Colombia and Peru. Only a tiny percentage of Bolivian cocaine is thought to reach the U.S., the world's largest consumer of the drug.

But officials say the increasing Bolivia-Brazil border traffic reveals Bolivia's growing coca crop and more sophisticated drug production feeding an expanding market in Brazil's largest cities and Europe beyond — both of which are beginning to catch up to the United States' traditionally much higher demand for the powder.

Most Bolivian drug labs are still humble operations where workers in rubber boots stomp on coca leaves to make a white paste to be shipped to Brazil for further refining into cocaine.

But police last month uncovered a vast laboratory in Bolivia's Santa Cruz state capable of producing 243 pounds of refined cocaine a day through "Colombian technology," said Col. Rene Sanabria, who directs Bolivia's Special Anti-Drug Force.

The site had an electric generator, microwave ovens to dry the cocaine powder, showers for the workers and hands-on direction from the world's largest cocaine producer: Six of the eight arrested workers were Colombian.

Another cocaine factory busted recently in Santa Cruz replaced the rubber boots of the coca steppers with machines and had a hidden airstrip to deliver the paste to Brazil, he said. "Now they use electric mulchers to reduce the time it takes to make the drug and obtain a higher percentage of the alkaloid."

Much of the Bolivian cocaine once passed through Brazil on its way to Europe, but now domestic consumption is booming. Police seized 34,833 pounds in 2005, more than twice the 14,330 pounds seized just a year before, according to the U.S. Embassy in Brazil.

In wealthy districts of Rio de Janeiro and Sao Paulo, dealers sell it through dial-up delivery services, while slum dealers cut the cocaine so severely with talcum powder or other mixers that a gram costs as little as $2, said Buzanelli, who estimates that more than 60 percent of Brazil's cocaine comes from Bolivia.

Bolivian coca production is still well below its mid-1990s peak but has rebounded steadily in recent years to an estimated 65,482 acres in 2005, from an estimated 36,077 acres in 2000, and the crop may expand more under President Evo Morales, who was elected by a landslide after promoting the coca leaf's cultural importance. While Morales has vowed to crack down on cocaine producers, he proposed nearly doubling the legal production limit to 49,420 acres.

Bolivia has spent $54.7 million in training, sport utility vehicles and helicopters for anti-drug patrols that seized 30,864 pounds of cocaine paste and cocaine last year, 23 percent more than the year before Morales took office. And Brazil has tightened controls on sulfuric acid, ether and other precursor chemicals for cocaine.

But just as with natural gas, Bolivia and Brazil's testy push and pull between supplier and consumer continues. As Buzanelli puts it, the Bolivian government sees cocaine as Brazil's problem: "Bolivia produces coca, and cocaine production is a problem of the countries that consume the drug."

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