A huge fire that has devastated swathes of southwestern France appeared contained on Friday as French and foreign firefighters worked flat out, but blistering temperatures made victory uncertain, local authorities said.

The 40-kilometre (25-mile) active fire front in the Gironde and Landes departments around Bordeaux had "not progressed for 48 hours", Gironde firefighting chief Marc Vermeulen said on Friday afternoon.

Some residents in two Landes districts were to be allowed home in the evening, and a highway section leading to neighbouring Spain was to be reopened for the first time in two days, local officials said.

Deputy prefect Ronan Leaustic told reporters earlier in the day that the fire had not developed, but the weather conditions were pushing officials towards "extreme vigilance".

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Huge fire in southwestern France / © AFP

Temperatures stood at 39 degrees Celsius (102 Fahrenheit) in the fire zone, just like the day before.

No new evacuations had been ordered on top of the 10,000 people already asked to leave, Leaustic added.

But "temperatures continue to rise and the water table keeps falling", he said.

EU members including Germany, Poland, Austria and Romania have pledged reinforcements totalling 361 firefighters to join the roughly 1,100 French ones on the ground, along with several water-bombing planes from the European Union fleet.

- 'Helping you guys' -

Many of the newcomers went into action on Friday.

"It doesn't matter which country we're in, we're firefighters, we are able to help people around the world," said Cristian Buhaianu, who commands a 77-strong firefighting contingent from Romania.

At the Merignac air base, near the southwestern city of Bordeaux, where Canadair planes and other firefighting aircraft are stationed, a Greek pilot said scenes of devastation like the ones seen in France were commonplace in his home country.

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France's neighbours are sending firefighters and planes to help out / © AFP

"We see this every year in Greece, and right now we see this in France," the pilot, 36-year-old Anastasis Sariouglou told AFP. "We have the feeling of helping you guys and it's nice."

Around 20 firefighters also flew over to help from French Polynesia.

In the hard-hit area around the village of Hostens, the thick smoke seen on Thursday gave way to blue skies and occasional clouds.

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How peat fires spread underground / © AFP

France has been buffeted this summer by a historic drought that has forced water use restrictions nationwide, as well as a series of heatwaves that experts say are being driven by climate change.

The blaze near Bordeaux erupted in July -- the driest month seen in France since 1961 -- destroying 14,000 hectares and forcing thousands of people to evacuate before it was contained.

But it continued to smoulder in the tinder-dry pine forests and peat-rich soil.

Officials suspect arson may have played a role in the latest flare-up, which has burned 7,400 hectares (18,000 acres) since Tuesday.

- 'Forced to adapt' -

Fires in 2022 have ravaged an area three times the annual average over the past 10 years, with blazes also active in the Alpine Jura, Isere and Ardeche regions this week.

The Ardeche fire "is far from under control, because the site is very difficult to reach", said Jean Jaussaud, a local emergency services commander.

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Fires in 2022 have ravaged an area three times the annual average over the past 10 years / © AFP

European Copernicus satellite data showed more carbon dioxide greenhouse gas -- over one million tonnes -- had been released from 2022's forest fires in France than in any summer since records began in 2003.

On Friday, 19 departments were still at the highest orange heat alert level set by weather authority Meteo-France.

This year's summer resembled predictions for "an average summer in the middle of this century" under pessimistic climate change scenarios, Meteo-France expert Jean-Michel Soubeyroux told AFP.

Maurin Berenger, a winegrower from the southwestern Lot department, said temperatures had been "unprecedented".

"We've been forced to adapt, we work from very early in the morning or even at night. I started at 3:00 am last night, and people with farm hands start at 6:00 to avoid the heat".

Weather forecasts suggest France's third heatwave this year will be broken by storms over the weekend.

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