Some members of Congress have also expressed concerns about the deal's impact on the U.S. pork business.

WASHINGTON — The U.S. Department of Justice’s Antitrust Division has requested additional information from Tyson Foods, Inc. about its proposed acquisition of the Hillshire Brands Co. The company said the request relates “only to a very small portion of the combined Tyson/Hillshire Brands business …”

The companies said they are working “expeditiously” to resolve the matter with the Antitrust Division. As a result of the request, Tyson Foods has extended its offer to purchase all of the outstanding shares of Hillshire Brands from Aug. 12 to Aug. 19.

The proposed acquisition also has come under criticism by members of Congress. Senator Chuck Grassley of Iowa on Aug. 7, for example, requested that the U.S. Department of Justice “heavily scrutinize” the transaction. In a letter to the Justice Department, Mr. Grassley said he was concerned about how the merger may increase concentration and decrease competition in the U.S. pork industry. He also said he was concerned about the impact on consumer choice and the price of pork.

“Independent, small producers have been to my office to express their own concern,” he said. “In particular, they fear that Tyson could engage in the practice of ‘tie-in’ sales of sows with market hogs, which would put independent producers at a tremendous disadvantage as they look for markets for their sows.”