WASHINGTON — The US 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. Sen. Chuck Grassley of Iowa on Aug. 7, for example, requested that the US Department of Justice “heavily scrutinize” the transaction. In a letter to the Justice Department, Grassley said he was concerned about how the merger may increase concentration and decrease competition in the US pork industry. He also said he was concerned about the impact on consumer choice and the price of pork. Grassley is the Ranking Member of the Senate Judiciary Committee, which has jurisdiction over anti-trust policy.

Tyson said the company is cooperating with the Department of Justice and willing to meet with Grassley to address his questions.

In July, Tyson Foods entered into an agreement to acquire Hillshire Brands for $63 per share. The all-cash transaction, which also includes debt, is valued at approximately $8.55 billion.