By Gary Duffy
BBC News, Sao Paulo
The Amazon is home to an estimated 39 isolated groups
The Brazilian authorities are to use a plane equipped with body-heat sensors to monitor uncontacted Indian tribes in the Amazon from a distance.
Brazil has a policy of leaving such isolated indigenous groups in peace unless it is absolutely necessary to make contact.
Officials say the plane will help them to protect remote communities without interrupting their way of life.
Some 39 isolated groups are believed to be living in the Amazon region.
In May this year the authorities released a photograph of members of an uncontacted tribe firing arrows at a passing plane - an image reproduced in newspapers and on websites.
It is thought there may be more than 100 such tribes still in existence worldwide - more than half living in Latin America.
Life for these isolated communities is often precarious.
In Paraguay the campaign group Survival International says land belonging to one such tribe is being destroyed by outside developers. Similar problems have been reported in Peru.
Now the authorities in Brazil are to adopt an innovative solution to monitor uncontacted tribes.
A plane fitted with body-heat sensors and flying at high altitudes will be used to locate them.
The Brazilian agency which oversees the welfare of indigenous people, known as Funai, says it will then be able to ensure that loggers and farmers are kept out of Indian territory.
As well as the threat to their land, diseases brought by outsiders pose a major risk to the health of these remote indigenous groups.
Without the plane, the work of locating the tribes has been enormously difficult and just confirming the existence of some of these communities will be a priority for the new service.
The majority of Brazil's indigenous population has greater contact with outside society, sometimes living in reservations where agencies provide health and other support, but their lives are often blighted by poverty and other social problems