International machinery firm Doosan Infracore Co. Ltd. has paid $647,500 to settle allegations of violating California’s clean-air laws, according to the California Air Resources Board.

ARB said the violations involved field modifications that Doosan field representatives made to emission-controlled 2010-12 heavy-duty compressed natural gas engines. Doosan officials disclosed the modifications immediately and cooperated with state officials, according to the ARB. The company operates throughout the state.

The emission-control system laws include provisions allowing manufacturers to address operational and durability issues, but proposed modifications must be documented and evaluated, and are subject to ARB approval.

ARB said $485,625 of the settlement will be paid to the California Air Pollution Control Fund, which supports efforts to decrease air pollution through education and the adoption of cleaner technologies. The remaining $161,875 was paid to help fund clean school bus and diesel engine emission-reduction projects.