(Bloomberg) -- Steel and aluminum tariffs imposed by the U.S. in March may already be filtering through to prices charged by American producers of the metals.

The cost of steel mill products climbed 4.3 percent last month, the biggest increase since February 2011, a U.S. government report showed Wednesday that

The report underscores concerns from metal buyers and economists that the tariffs could raise costs of goods ranging from cars to construction equipment. It also helps explain why American steelmakers’ stocks have been rising. Double-digit-gains in shares of Irving, Texas-based Commercial Metals Co. and Steel Dynamics Inc. of Fort Wayne, Indiana, led an advance in the Bloomberg Americas Iron/Steel Index in May.

A global gauge of iron and steel producers tracked by Bloomberg Intelligence fell last month, led by declines in Chinese companies.

--With assistance from Vince Golle.

To contact the reporter on this story: Joe Richter in New York at jrichter1@bloomberg.net

To contact the editors responsible for this story: James Attwood at jattwood3@bloomberg.net, Joe Richter, Luzi Ann Javier

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