"Two starts of fires" 1.5 km apart were triggered in the municipalities of Saint-Bauzille-de-la-Sylve, Gignac and Aumelas, before joining, in an area "difficult to access" and sparsely populated composed of scrubland, holm oaks and vines.
"No casualties are to be deplored," said the prefecture.
Some 130 people were evacuated as a preventive measure in the town of Aumelas, as well as 150 people who were gathered for a wedding. Fifty of them were able to find refuge in a village hall, said the same source.
"The propagation conditions are very unfavorable" with very dry vegetation, said the sub-prefect of Lodève Eric Suzanne during a press conference, adding that the fires had been "pushed by a strong wind".
The objective is to "fix the fire" by 10:00 p.m. and the arrival of night which prevents rescue planes from flying over the area for security reasons.
"The wind will drop with the night normally, so there will be a relative calm", however nuanced Mr. Suzanne.
"A judicial investigation has been opened on a criminal hypothesis," Montpellier prosecutor Fabrice Bélargent told AFP.
The commander of the relief operations, Colonel Sylvain Besson, spoke for his part of the departures of fires "probably malicious".
"We think it's criminal, it's disastrous," reacted the mayor of Gignac Jean-François Soto, recalling that a Natura 2000 area for the preservation of biodiversity was nearby.
"When you see all the efforts we make, all the means we put (...) and the result in the end, it's hard," he commented.
“In total, nearly 600 firefighters are fighting the flames. Three water bomber planes (two Canadair and a dash) are also deployed, as well as two planes from the departmental cell of the Hérault firefighters.
"We are working hard. The fire is not under control," said the sub-prefect.
A noria of yellow and red civil security planes took turns to put out the fire, the smoke from which was visible from the highway, AFP journalists noted.
At the request of the firefighters, two high and very high voltage lines were cut in the evening but without this having any consequences for the residents, RTE, network manager, told AFP.
- Intensification of fires and droughts -
In addition to the megafires in Gironde which destroyed thousands of hectares of forest, several fires also affected the south-east of France this summer. Last week, 150 hectares had been destroyed in Hérault and Aude. In the neighboring department of Gard, some 650 hectares of forest had also been ravaged in early July, while 1,600 hectares burned south of Avignon in mid-July.
The Hérault department was on Tuesday in "high" to "very high" fire risk depending on the massifs.
If summers are dry in the South, with global warming, the intensity of these episodes of drought is likely to increase further, according to UN climate experts.
In France, with global warming, "the activity (of the fires) will intensify in the areas where it is already strong, in the South-East", underlined Jean-Luc Dupuy, expert at the National Institute of research for agriculture, food and the environment (Inrae) at the end of June.
The risk of fire is maximum in France after a wave of heat wave. Ninety departments out of 96, a "record", are subject to restrictions on the use of water on Tuesday.
The forest fires that have raged in Europe in recent weeks, particularly in the west of the continent hit by heat waves, have already affected more area than during the whole of 2021, according to the European specialized monitoring service.
