Lawmakers have called on the Department of Justice to investigate whether Mylan violated the law by misclassifying its severe allergy treatment EpiPen as a generic in the Medicaid Drug Rebate Program.

In a letter, Senate Judiciary Committee Chairman Charles Grassley (R-Iowa) and two of the committee’s Democrats—Sens. Richard Blumenthal (Conn.) and Amy Klobuchar (Minn.)—asked Attorney General Loretta Lynch to look into whether the company knowingly misclassified the product so it could pay states a lower percentage of its EpiPen revenue.

The Medicaid Drug Rebate Program requires that makers of new drug products pay states a minimum rebate of 23.1 percent, but Mylan evaded these payments through the misclassification of its EpiPen and paid the 13 percent rebate levied on generics, the senators said.