PARIS - Swiss army helicopters have crossed the Franco-Swiss border in an unexpected incursion - to help thirsty Swiss cows.

The aerial operation to scoop up water caught authorities responsible for Rousses Lake in the Jura mountains by surprise last Thursday. The helicopters also startled swimmers and fishermen enjoying the beaches of the lake in eastern France.

Christophe Mathez, deputy mayor of the Les Rousses commune, said officials had "no idea this operation would occur" - and that the Swiss neither requested authorization or nor warned before descending.

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Swiss media reported that the country's military did ask for permission - but from the French air force, not local authorities or the police.

"As soon as they contacted us, we realized there was a communication problem and we immediately stopped," Denis Froidevaux, a Swiss military official, told the Swiss newspaper Le Matin, whose headline Monday read "No, Switzerland is not stealing water from France to save its cows."

Mathez said Les Rousses authorities are not "mad at our neighbors," but as of Monday the village was still waiting for clarification.

The Swiss army has been pumping water for livestock from its own Neuchatel and Joux lakes since last week, according to a statement from the Swiss Department of Defense. The federal government is bankrolling the operation, expected to continue no longer than August 4, with military aid disaster relief funds.

Thirsty cows produce less milk, of particular concern in the mountainous Jura region of France and Switzerland. Dairy farmers there provide milk to producers who make prized cheeses including the French Comte and Morbier varieties as well as the Swiss Tete de Moine.