The giant blaze broke out initially at Pedrogao Grande and spread to adjacent areas including Gois, Pampilhosa da Serra and Arganil.
The fire in Pedrogao Grande, which ravaged 30,000 hectares (74,000 acres) of forests, was doused only late Wednesday.
The blaze in Gois, the second biggest after Pedrogao Grande, was brought "under control" on Thursday, said Carlos Tavares, the civil protection official leading the operations, though he cautioned that some fires could resume.
Press reports have suggested that Portugal's fire plan had not been revised for four years and that the intense heat might have made some communication antennae malfunction.
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The president of the League of Firefighters, Jaime Marta Soares, said Wednesday that he believed arson had caused the fire, contradicting an earlier account by police.
On Sunday, police chief Almeida Rodrigues had ruled out arson, blaming dry thunderstorms for the blaze after saying they had found a tree hit by lightning.
But Marta Soares told local news media the fire had already been burning for two hours before the storm started Saturday.
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