More U.S. senators on Friday raised concerns about a Chinese company's plan to buy U.S. pork producer Smithfield Foods Inc, particularly in light of restrictions that China continues to place on imports of U.S. meat.

"The purchase of Smithfield - the largest pork producer in the world - is difficult to square with China's restrictive policies that effectively ban U.S. pork," the top Democrat and Republican on the Senate Finance Committee said in a letter to U.S. Treasury Secretary Jack Lew.

"This review must be thorough and take into account the full range of national security interests. In particular, we urge that due consideration be given to the impact of the transaction on food safety in the United States," added Senators Max Baucus of Montana, the committee's chairman, and Orrin Hatch of Utah.