Tavares said the suspect's name was Clodoaldo Carlos Batista, also known as "Eduardo," but local news agencies said his name as Uilquelano Pinto.
Police are bringing the suspect in the contract killing to Altamira, a larger town in Para on the Xingu River. Rayfran das Neves Sales, another suspect, confessed to shooting Stang earlier this week and named others involved.
Brazil has launched its biggest crackdown on crimes committed in the rainforest after Stang's murder drew international outrage at death-squad killings and deforestation in the Amazon state of Para. Last week, the federal government sent 2,000 troops to lawless areas of Para and set up a crisis Cabinet in the state when three rural workers were killed in the three days following Stang's murder.