(AP & WHAM 1180) Shares of locally based Constellation Brands fell sharply Thursday morning after the U.S. Justice Department filed an antitrust lawsuit challenging Anheuser-Busch InBev's proposed $20.1 billion purchase of Mexican brewer Grupo Modelo, which would unite the ownership of popular beers such as Bud Light and Corona.

That harms the chances of Constellation's related $1.85 billion deal that would land it greater U.S. control of Corona and other beers. Constellation was to buy the remaining half of a joint venture with Grupo Modelo, Crown Imports LLC, that imports Modelo beers into the U.S.

The deal with Constellation was intended to alleviate antitrust concerns. But the Justice Department says that it wasn't enough to protect U.S. beer buyers.

Constellation Brands Inc. shares lost 20 percent early Friday morning.

The company issued the following statement:

"Constellation Brands is disappointed with the DOJ decision. The proposed transaction would further establish Crown Imports as a more independent and competitive entity and solidify its position as a major player in the U.S. beer industry. We will provide further comment when appropriate. 

Given today’s development, we no longer expect the deal to close during the first calendar quarter of 2013 but we ultimately look forward to an expeditious resolution."