Alcoa Inc., the largest U.S. aluminum producer, was cut to junk by a second ratings company as a global oversupply of the metal hampers profitability.

Fitch Ratings cut Alcoa’s credit grade one level below investment grade to BB+ from BBB-, it said today in a statement. It sees Alcoa’s total debt remaining more than 2.5 times its earnings before interest, taxes, depreciation and amortization.

Alcoa is working to reduce dependence on the price of raw aluminum by shutting high-cost smelters and boosting sales of specialized shapes and alloys for customers in growing industries such as aerospace and autos.

The company was cut to junk by Moody’s Investors Service in May. Standard & Poor’s Ratings Services rates its debt BBB-, the lowest investment-grade level. New York-based Alcoa was removed from the Dow Jones Industrial Average on Sept. 10 after 44 years.

“Alcoa is aggressively transforming the company -- building out our value-add businesses and improving our competitive position by lowering the cost base of our commodity business,” the company said today in an e-mailed statement. “Our debt is at the lowest level it’s been since 2007, and we have no significant maturities due before 2017.”

Fitch said that this year and next it expects Alcoa’s profit to continue to reflect weakness in the price of aluminum, as its debt-to-Ebitda ratio rises to as much as 2.9.