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, said.
The blaze engulfed a sawmill and burned 10 vehicles.
"We are awaiting reinforcements," said regional deputy fire chief Jean-Jacques Peraldi. Around 160 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 affected".
Another fire on the south of the island, which destroyed 110ha 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 800ha by late Monday. Firefighters said they had been unable to keep the flames under control.
Around 100 homes in the village of Mirabeau and a neighbouring hamlet had to be evacuated, according to officials. Up to 500 firefighters were expected on the scene.
In the nearby Var region, another fire burned over 200ha 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."