A Brazilian judge has issued a warrant for the arrest of three men accused of the murder of a US Catholic missionary and human rights activist.
Dorothy Stang was shot at point-blank range
The authorities believe Dorothy Stang, a 74-year-old nun, was the victim of a contract killing because of her work defending Amazon peasant farmers.
Witnesses said she was shot at close range by two gunmen at an isolated jungle settlement in the state of Para.
Police say the killing on Saturday came after a series of death threats.
They have not released the full names of the suspects, but they have said they believe the two gunmen were hired to carry out the crime and that others are involved.
Sister Dorothy was a member of the Congregation of the Sisters of Notre Dame de Namur, an international Catholic religious order, and had lived in Brazil for more than 30 years.
Based in the rural town of Anapu in the state of Para, she became known as an outspoken critic of ranchers and loggers trying to encroach on peasant farmers' land.
She recently won an award from the Brazilian lawyers' association (OAB) for her work in the Amazon region, while the state authorities named her woman of the year.
Environment Minister Marina Silva, who knew Sister Dorothy personally, compared her murder to the killing of trade union leader Chico Mendes, a rainforest campaigner whose death in 1988 sparked worldwide outrage.
Brazilian President Luiz Inacio Lula da Silva has sent ministers and police teams to the area to bring her killers to justice.
Sister Dorothy's body was flown to the state capital, Belem, on Sunday for a post-mortem examination and will return to Anapu for burial on Monday.