Colonel Eric Martin of the Var firefighting unit said on BFM-TV that almost 600 firefighters were trying to contain the flames that have torn through 1,300 hectares (3,210 acres) of woodland in his area alone.
Local authorities said that while it was safe for people to return to places they'd evacuated in the Bormes-les-Mimosas area, the fire risk remained at its highest level in other parts of the Var region.
The president of the Provence-Alpes-Côte d'Azur region said it was "unlikely" that the Bormes-les-Mimosas fire was accidental, and according to the Delegation for the Protection of the Mediterranean Forest, around 39 percent of the fires are thought to have been started by arson.
Thousands of firefighters were deployed to the region when the fires broke out on Monday and water-dropping planes conducted dozens of sorties over the area.
Thousands of people were evacuated and huge areas of vegetation destroyed by forest fires which have raged in south eastern France and Corsica over the past week. Among those affected were the hordes of tourists who descend on the popular vacation destination every year. More than 2,300 firefighters with over 700 vehicles battled 13 blazes, with flames driven by powerful winds.
Still, the Var prefecture said fires in some sites in Bormes-les-Mimosas mean it is "not yet possible" for displaced residents and tourists to return to their homes and campsites.
Arsonists blamed as blazes on French Riviera force thousands to flee
In central Portugal on Wednesday, billowing smoke made visibility too poor to use water-dropping aircraft on the region's flaming pine and eucalyptus forests.
The worst-hit areas were located 200 kilometers (125 miles) northeast of Lisbon, where the fires briefly forced the evacuation of some hamlets and the closure of a section of highway. Last month, 64 people died in a wildfire.
Local fire chief Philippe Gambe de Vergnes later said the fire had been contained.
Nearly 2,000 firefighters were deployed at six major blazes across Portugal Thursday.
The Portuguese Civil Protection Agency says Wednesday that emergency services have brought more than 20 other forest blazes under control as high winds calmed down during the night.
The statement said that some 10,000 people - about 3,000 of them campers - were evacuated from La Londe and nearby Bormes and La Lavandou.