AUGUSTA — A national trucking industry group filed a lawsuit Friday in an attempt to block a new law that will levy special fees for transporting hazardous materials on tens of thousands of trucks that currently are exempt.

The Virginia-based American Trucking Associations Inc. and the New Jersey-based TNT Red Star Express Inc. maintain in their class-action suit that the law is unconstitutional because it interferes with interstate commerce and unfairly favors Maine-based trucks.

An attorney for the state dismissed the claims as groundless and expressed optimism that the law would be upheld in court. The lawsuit was filed in Superior Court in Augusta.

“We think the suit is without merit,” said Deputy Attorney General Thomas D. Warren.

The law in question, which takes effect July 1, would greatly expand the scope of the fees, which generate money for training, equipment and other costs associated with cleaning up spills of hazardous materials.

Currently, the fees apply only to a limited number of hazardous materials and are set at $50 per year for any truck hauling more than 2,000 pounds of those materials, said Gary R. Hinkley, director of the commercial vehicles center of the secretary of state’s office.