NEW YORK — U.S. Steel Corp. has increased spot market base prices for carbon flat-rolled steel products by $50 per ton effective immediately, according to an internal memo dated Feb. 26.

"This increase is applicable to all open quotes and/or negotiations where an agreement is yet to have been concluded, and pricing extras, as published on our corporate website, will continue to be fully applied," the memo said.

AK Steel Corp. followed Feb. 27 with a $50-per-ton increase in spot market base prices for all carbon flat-rolled steel products effective immediately. The West Chester, Ohio-based steelmaker did not give a reason for the increase.

Sources said that other mills were mulling similar moves.