"There are no more intruders in the region," Marcos Antonio Farias, Federal Police chief in the Mato Grosso capital Cuiaba, told Reuters.

Those arrested belonged to an association of landowners seeking to develop the area known as Rio Pardo into farmland. The territory has been earmarked but not officially declared an Indian reservation by the government.

"This is an isolated Indian community with no contact to the outside world so we may never have definitive proof but there are strong indications that these criminals were seeking to exterminate them and take their land," Mario Lucio Avelar, Mato Grosso public prosecutor, told Reuters.

During an expedition this year, the government's National Indian Foundation (Funai) officials found the squatters armed with guns and bombs, a Funai spokesman said. They also found instruments and makeshift shacks of the Indians.

Almost nothing is known about the Indian community - neither the language they speak nor the tribe they belong to.

Nobody has ever communicated with it but last month's Funai expedition sighted a few members.

A cameraman, documenting the expedition, filmed the attempted contact with one Indian accompanied by two women, who was cutting a tree trunk in search of honey.

After hesitating, the Indian put down his weapon but fled when the Funai guide held out his hand to greet him.

Avelar said officials in the state's land registrar had participated in the land appropriation scheme by issuing false land titles in the area.

Anthropologists have identified 30 groups of Indians that have made no lasting contact with the outside world. The government's policy is not to establish relations with such communities unless they are deemed to be in danger of extermination.

Brazil's native Indians account for only 0.2 percent of the 180 million population. At least on paper, they hold 12 percent of the country's territory, an area larger than Germany and France together.

Yet in practice the Indian territories often do not provide the necessary protection or well-being for their survival. In some cases land speculators and wildcat miners invade the territories. In other cases, corrupt Indian leaders sell the rights to use their natural resources.