The probe, focused on whether Canadian producers received subsidies allowing them to sell their paper in the US market at a cut rate, could result in anti-dumping and countervailing duties.
The department said in a statement it had received a complaint from a paper company in the northwestern United States, which alleged that Canadian products had sold from between 23.5 percent and 55 percent below market rate.
The value of uncoated groundwood paper imports to the US from Canada was an estimated $1.27 billion last year, according to the statement.
The US has already slapped tariffs on Canadian softwood lumber as part of a trade conflict between the neighboring countries.