RIO DE JANEIRO, Nov. 19 (Xinhua) -- The expansion of biofuel production should not be blamed for rising food prices, according to a study released on Wednesday by a Brazilian private research center.

    Alexandre Mendonca de Barros, an economist with the Getulio Vargas Foundation, who chaired the study, said speculation in the future markets was a "true cause" of the food price rises in 2007 and 2008.

    The study showed that price increases were mainly caused by speculation, and while the speculative activities increased, the prices rose.

    According to the study, the hedge funds targeting agricultural commodities increased 48 percent between 2005 and 2008, and in the last two months, when food prices fell, the speculators "disappeared".

    The low level of stocks was alleged to be another reason for the high food prices, as well as the strong increase of the demand for grains, especially in emerging countries.

    The study also mentioned at the first International Conference on Biofuels in Sao Paulo, Brazil.