The two men went missing in the rainforest near Brazil's border with Peru on Sunday.
No trace has been found of them or the boat they were travelling in.
The lead investigator said his team was "pursuing all lines of inquiry".
There has been huge concern for the welfare of the men after it emerged that Mr Pereira had received death threats in the week before they went missing.
Brazilian football legend Pelé is among those who have urged the authorities to intensify to scale up their search.