Soybean production in the Brazilian state of Amazonas has increased by 425 percent in the five years to 2006, causing a major expansion and deforestation in jungle areas, a research body said Sunday.

The 2005-2006 harvest was 8,400 tons, up from 1,600 tons in the 2001-2002 season, Fepam, the Amazonas State Research Support Foundation, said in a report.

According to ecological groups, soybean farming's incursion is the biggest threat to the Amazon forest, which is regarded as the lungs of the Earth.

Fepam said soybean farming has already had an environmental impact on three administrative regions of the state -- Apui, Humaitu and Manicore.

"Soybean prices are set by international markets and if prices rise, the Brazilian production rises too," said Elane de Oliveira, a Fepam researcher who worked on the study.

Prices "lead to the expansion of the cultivated area and areas that have already been degraded, just as much as in virgin forest," she said.

Brazil is the world's top soybean exporter and the second largest producer.