PARIS - Massive floods caused serious damage and power outages on Friday in parts of France's mountainous southeast region after days of heavy rain, though there were no immediate reports of any casualties.

France's weather authority Meteo France placed six departments south of the city of Lyon on a red flood alert on Thursday. The alert was downgraded to 'orange' on Friday, indicating that water levels would come down again.

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"At certain places in the Ardeche region, up to 700 milimetres of water has fallen in 48 hours. That's more than a year's rainfall in Paris, so it's absolutely gigantic," Agnes Pannier-Runacher, the environment minister, told BFM TV.

French news stations showed cars, traffic signs and cattle being swept away by the floods. The A47 highway close to Lyon was temporarily transformed into a giant stream of water.

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The French interior ministry said Paris had dispatched 1,500 additional firefighters to the affected areas.