Officials in Paraguay say at least four indigenous people have been killed by drug traffickers in a remote region bordering Brazil since August.
Governor of Amambay province Juan Ramirez said the men had been murdered for witnessing landings of light aircraft used to smuggle drugs.
Mr Ramirez travelled to Amambay after the Pai Tavytera tribe asked for protection.
Tribe members told him traffickers shot one man as recently as last Friday.
They said more than a dozen armed men came to their village and threatened a massacre unless they handed over $1.8m (£1m) the traffickers had lost when one of their planes crashed in the jungle.
The villagers told investigators they heard the plane crash in bad weather in September, but denied having found the wreckage, or any money inside.
Police found the empty plane on Monday around 1km (less than a mile) from the village.
They said there were signs that heavy vehicles had entered the area and removed evidence from the plane, including its engines.
Tribal leader Elba Ramos Valiente told Mr Ramirez how Lucio Quevedo, 22, was murdered by gunmen in August after he surprised them unloading drugs from a plane.
She said three more indigenous people had been killed since, allegedly also for witnessing drug smuggling in the area.
Police originally suspected cattle thieves of those murders.
The area is used for smuggling cocaine and marihuana from Colombia and Bolivia to Brazil and on to Europe.