Brazilian police are investigating the possibility that Sir Peter Blake was murdered because of his environmental stand.
One of Brazil's largest newspapers said investigators were checking whether his death had any links with alleged death threats that the world-famous sailor and conservationist received.
O Estadao de Sao Paulo said sources in the intelligence section of the federal police had confirmed that Sir Peter received threats days before he was shot dead.
Six men allegedly involved in the raid on his vessel Seamaster are due to appear before a judge today.
The newspaper said that officially the federal police were saying the attack was "latrocinio" - robbery followed by murder.
A stash of firearms had been found near the scene of the shooting and investigators were trying to find out who they belonged to.
Last year, Sir Peter said he had received death threats. "We've always got crank mail but it has been going beyond that recently," he said.
In 1988, Brazilian conservationist Chico Mendes was shot by farmers opposed to his efforts to protect rainforests.
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Brazil probes death threats against Blake
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