A Peruvian forensic expert says a British Catholic missionary and environmental activist died before his body was burned at a youth hostel he ran in the Amazon region.

Loreto region chief forensic doctor Francisco Moreno told The Associated Press that that no carbon dioxide was found in Paul McAuley's blood, ruling out burning as the cause of death.

The 71-year-old missionary was found death on Tuesday at the shelter he founded for indigenous schoolchildren.

Prosecutors have not yet said if McAuley was murdered or what the motive might have been. They have been collecting evidence and interviewing the students.

Moreno said Thursday that additional tests are being carried out.

In 2004, McAuley and environmentalists opposed then-President Alan Garcia's moves to open up the Amazon to mining and oil exploration.