4 p.m.Following months of industry rumors and speculation, the owners of Calistoga’s Chateau Montelena Winery have sold their respected 40,000 case operation to a revered second-growth Bordeaux wine estate, Chateau Cos d’Estournel.

Spokesmen for Michel Reybier, owner of the Saint-Estèphe winemaking operation, and Chateau Montelena owners Jim and Bo Barrett, said a “firm” deal was reached Tuesday, with regulatory approval of the change of ownership of the medieval-styled stone facility expected by fall.

Jean-Guillaume Prats, general manager of Cos d’Estournel, would neither confirm nor deny a rumored $110 million had been paid for the Napa Valley winery and its vineyards. A spokesman with the Calistoga winery indicated sales figures being bandied about were inaccurate.

“It’s the kind of investment that would be similar to buying a top Bordeaux estate,” Prats told European news organizations.

According to Vic Motto, Global Wine Partners CEO who helped broker the deal, Reybier puts his new wine holding on a par with the best of Bordeaux.

The sale of Chateau Montelena comes about a year after another pair of celebrated Napa Valley wine operations were sold to European wine houses. Stags Leap Wine Cellars and Duckhorn Wine Company were sold in 2007 for $185 million and a reported $250 million or more, respectively.

Chateau Montelena and Stags Leap Wine Cellars popped up on the world’s wine radar when a Montelena chardonnay and a Stags Leap cabernet sauvignon beat out their French counterparts in a celebrated comparative tasting in Paris in 1976.

News of the sale comes just days before the Napa Valley premiere of the movie “Bottle Shock,” which reportedly recounts events leading up to and during the so-called 1976 Judgment of Paris tasting. The Barretts, their winemaker at the time, Mike Grgich, and Stags Leap Wine Cellars owner and winemaker Warren Winiarski would become well known throughout the industry and by consumers following the legendary wine competition.