Members of the Matis Indian tribe found the plane and the survivors in a sprawling jungle reservation, the air force said in a statement.

One person abroad the single-prop Cessna Caravan plane was missing and another may have died in Thursday's emergency, the air force said. It did not say why the plane was forced to set down on the Itui River.

Rescue teams were being sent to the roadless site near several Indian villages close to Brazil's border with Peru.

The plane carried four crew and seven members of a government medical team who travel by plane and boat across the Amazon vaccinating rain forest dwellers who can't be reached any other way.

The plane took off Thursday morning from the small city of Cruzeiro do Sul in Acre state. It was scheduled to land about two hours later in the city of Tabatinga in Amazonas state.

The plane went down in the Vale do Javari reservation, one of Brazil's largest. It is home to several tribes, some believed to have never had contact with civilization.