U.S. seeks more data from Bemis on Alcan buy

* 'Second request' could signal divestment requirement * Bemis shares slightly weaker; Rio Tinto up in London NEW YORK, Sept 17 (Reuters) - U.S. food packager Bemis Co said on Thursday that the U.S. Department of Justice had requested additional information about its planned purchase of Rio Tinto's U.S. packaging arm. Miner Rio Tinto announced in July that it would sell the Food Americas business of its Canadian aluminum and packaging unit Alcan to Bemis for $1.2 billion. The "second request" from the DOJ, which is conducting the regulatory review of the acquisition, could indicate that Bemis might have to divest some of its operations in order to win approval for the deal, one analyst said. "We believe that the area of particular interest relates to Bemis likely dominating the market for packaged meats and cheeses," analyst Ghansham Panjabi of Robert W. Baird wrote in a note to investors. The purchase would lift Bemis above rival Sealed Air Corp as the top flexible packager in North America by market share, and is seen as critical for Rio Tinto to reduce debt it accumulated when it bought Alcan in 2007. Shares of Bemis were down 0.4 percent at $27.34 in morning trading on the New York Stock Exchange. Rio Tinto's London shares were up 0.2 percent at 2730 pence. (Reporting by Matt Daily; Editing by Lisa Von Ahn)