The suspects could face lengthy prison time if they are found guilty of manslaughter, The Portugal News reported.
The latest victim of the fires was Bernardo Figueirdo, 23, who was buried Tuesday, the News said.
Authorities said fires burned through 98,000 acres of forest this month.
The fire starters are usually male, between the ages of 16 and 45, have only had a few years of schooling and reside in the area where a fire was started, officials said.
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