A big merger in the flour business that involves two Minnesota companies is not expected to be completed until 2014's first quarter, partly because of an ongoing antitrust review.

The deal's closing is being delayed from its original expected completion date of the end of 2013, ConAgra Foods said in a regulatory filing late Monday.

Omaha-based ConAgra is combining its flour business with those of Minnetonka-based Cargill and Inver Grove Heights-based CHS. The new company, called Ardent Mills, is expected to be based in Denver.

Ardent will be the largest U.S. flour producer by far. Cargill and CHS already combine their flour operations in a joint venture called Horizon Milling, which has about 18 percent of the market. ConAgra has about a 16 percent share.

The U.S. Department of Justice's antitrust division acknowledged last July it was investigating the Ardent merger.

ConAgra has revised the closing date "due to various reasons, including the ongoing regulatory review process and discussions with the U.S. Department of Justice," the company said in a filing with the Securities and Exchange Commission.