It’s a ripening mystery: Who’s stealing the wine grapes of Germany?

Thieves raiding lucrative southern German vineyards have made off with a minor fortune in fruit over more than a dozen forays under the cover of darkness.

Vintners have increased their vigilance, posted guards and sought help from the police, but so far, the thieves have made off without a trace.

“They picked off more than 2,500 kilograms of my best red grapes,” said Stephan Attmann, who runs a vineyard near Deidesheim in southwestern Germany.

“It hurts, not just financially, but also emotionally,” Attmann said. “We had spent weeks preparing the vines, getting rid of all the sour grapes, and then they came one night and stole everything.”

Attmann estimates his losses so far this season at some euro100,000 ($137,700) — more than 3,000 bottles of high-class Pinot Noir selling for euro32 a bottle. He said he did not have any kind of insurance that covered the losses.