U.S. Commerce Secretary Wilbur Ross said on Wednesday his agency is launching an investigation of recent steel price hikes to determine whether some market participants are "illegitimately profiteering" from new U.S. tariffs.

Ross told a Senate Finance Committee hearing that the price of steel in the U.S. market has risen far more than justified by the 25 percent tariff, possibly because of "speculative activity" with some market intermediaries holding back inventories.