Rio de Janeiro - A huge fire engulfing a swath of Brazilian jungle threatens the existence of remote indigenous tribes and may have been started by illegal loggers invading the territory, Greenpeace said on Wednesday.About 12 000 members of the Guajajara tribe and 80 people from the even more isolated Awa-Guaja live on lands affected by what the environmental group described as "one of the biggest forest fires ever registered within an indigenous territory in Brazil."Already burning for two months, the blaze has consumed at least 45% of the 413 000ha Arariboia Indigenous Reserve in Maranhao state, on the edge of the Amazon jungle, Greenpeace said.The burned area is approximately equivalent to 190 000 football pitches.Aerial footage released by the group showed smoke billowing from multiple places in the jungle and helicopters attempting to control the flames by dumping chemical extinguishers."It was shocking to see the gigantic dimensions of the destruction and to see that the Gaujajara and Awa-Guaja are the great victims of this tragedy," Greenpeace activist Danicley de Aguiar said in a statement."Beyond putting out the fire, the main worry is guaranteeing the survival of these peoples."About 250 firefighters are attempting to control the blaze, controlling a fire line more than 100km long.The area has been the scene of tensions between indigenous inhabitants and illegal Brazilian logging companies. "Loggers are being accused of starting the fire as a reprisal," Greenpeace said. "Along with other indigenous territories in Maranhao, the Arariboia suffered invasion and systematic theft of wood."