Sister Dorothy Stang, 74, of the Sisters of Notre Dame de Namur, was shot several times Feb. 12 while traveling to meet officials from the National Institute of Colonization and Agrarian Reform.
Those accused are farmers Vitalmiro Bastos de Moura and Regivaldo Pereira Galvão, suspected of having ordered the slaying; foreman Amair Feijoli, accused of being the intermediary; and farmers Rayfran das Neves Sales and Clodoaldo Batista, who have confessed to the murder.
The prosecution of the state of Para believes the motive behind the killing is that the farmers were opposed to her work in agrarian reform in the Amazon.
If convicted, the accused could be sentenced to 30 years in prison.
In June, the U.S. Justice Department indicted Rayfran das Neves and Clodoaldo Batista in connection with the same crime.
Sister Stang, a naturalized Brazilian citizen, was born in Ohio.