Police on Sunday leveled a charge of conspiracy to murder against a man suspected in the killing of American nun Dorothy Stang (search), who tried to protect the Amazon and its poor residents from loggers and ranchers, authorities said.

Amair Freijoli da Cunha, known as Tato, was charged after nearly three and a half hours of interrogation with Para state police in Altamira (search), a city about 80 miles from where the 73-year-old nun was shot dead on Feb. 12, police said.

Cunha had turned himself in Saturday after arrest warrants were issued for him, the two purported gunmen and a rancher accused of ordering the slaying.

Cunha, who was accompanied by a lawyer, denied involvement in the crime, but police said he gave too many contradictory statements. His connection with the other suspects was clear, police said.

Police investigator Waldir Freire said there was indication that Cunha "was lying the whole time," the official Agencia Brasil (search) news agency said.

If convicted, Cunha faces up to 30 years in prison.

Also Sunday, witnesses told police that Cunha and Stang had an altercation a day before she was shot six times at the Boa Esperanca settlement near the rural town of Anapu, about 1,300 miles north of Rio de Janeiro.

Police said Stang, a naturalized Brazilian from Dayton, Ohio, wanted Cunha to leave the settlement, where she helped some 400 families survive in the rugged jungle.

Other details about the altercation were not immediately known, police said.

Cunha allegedly hired the gunmen on behalf of rancher Vitamiro Goncalves Moura, known as Bida, police said. Authorities claim Moura ordered the killing.

Moura and the two gunmen were still at-large, police said. State and federal officers and jungle troops in helicopters and pickup trucks were hunting for them in the largely lawless Amazon region where Stang was killed.

Stang spent more than 20 years helping protect the rain forest and local peasants.

Lawlessness has long been common in the Amazon state of Para, where ranchers, backed by hired gunmen, ensnare poor workers in an endless cycle of debt akin to slavery.