(CNN) At least 10 people have died after flash flooding hit the Aude region of southern France, local officials said Monday.

Roads were cut off and cars overturned after three months' worth of rain fell in six hours overnight Sunday into Monday, causing rivers to flood.

An 88-year-old nun was killed after water swept through a nunnery in Villardonnel, while four people died overnight in nearby Villegailhenc.

The death toll was lowered by the Ministry of the Interior, after initially being placed at 13. Another person is missing and five are seriously injured, officials said.

Seven hundred firemen and seven helicopters have been mobilized in response to the flooding, which has reached unprecedented levels in the Aude valley, according to France's flooding watchdog, Vigicrues.

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