The fire was "almost certainly arson," he said.
Two water-dropping planes and 80 firefighters, helped by 50 volunteers, were tackling the blaze, which broke out overnight Monday near Pisa in northern Italy, briefly threatening the towns of Calci, Montemagno and San Lorenzo e la Torre.
Some 500 inhabitants were evacuated as olive trees burned in their groves and the sky across the area turned a deep orange, according to an AFP photographer at the scene.
On Tuesday the region's four firefighting helicopters were grounded to the strong winds.
Tuscany's governor Enrico Rossi said evacuated locals would not be able to return for 24 hours while risk assessments were carried out.
"The firefighters were our angels. It was an apocalyptic scene and thankfully they saved us," one evacuee was reported as saying by Italian media.
"I really hope the blaze was carelessness because I can't bear to think it could have been such an evil act by such a twisted mind."