The companies said Sept. 18 that Smithfield Foods, based in Smithfield, Va., would buy Kansas City-based Premium Standard Farms in a cash-and-stock transaction valued at $810 million.

In a release Friday, Smithfield that the Justice Department's Antitrust Division has exercised its option to take an additional 30 days to review the proposed transaction. The review period ends on May 7.

Premium Standard Farms produces pork products for retail, wholesale, food service, export and other processor markets. The company bills itself as the nation's second-largest pork producer and sixth-largest pork processor. It has about 4,300 employees at farms and processing facilities in Missouri, North Carolina and Texas.

For the year that ended June 24, the company reported earnings of $45.3 million on sales of $880 million.

With annual sales of $11 billion, Smithfield is the leading processor and marketer of fresh pork and processed meats, and the largest producer of hogs, in the United States.