Residents were evacuated from homes at the edge of the town of Biguglia, on the island's northeastern coast.
"The fire is very fierce and heading to urban areas of Biguglia," lieutenant-colonel Michel Bernier, of France's civil defence forces, told AFP.
The blaze engulfed a sawmill and burned 10 vehicles.
"We are awaiting reinforcements," said regional deputy fire chief Jean-Jacques Peraldi, adding that around 150 people were battling the blaze aided by more than a dozen fire engines.
Local official Gerard Gavory said that three firefighting planes were also involved, and "have been surveying the area to make sure no homes are effected."
Another fire on the south of the island, which destroyed 110 hectares around the town of Aleria, was brought under control on Monday, Bernier said.
Elsewhere in France, a fire raged in the forests around Luberon in the Vaucluse region, covering 650 hectares.
Several homes in the village of Mirabeau had to be evacuated, according to officials.
In the nearby Var region, another fire burned over 200 hectares at Gigaro, close to the Mediterranean resort of Saint-Tropez.
Another blaze in Carros, north of Nice, burned a house, three vehicles and a warehouse and led to some homes being evacuated, according to regional authorities.
More than 270 firefighters were on the scene.
"It's a very dangerous day," Bernier said. "And the fight is going to be very, very long tonight."
