Two Mexican officials say a large-scale firefight broke out Friday when federal forces came under fire in an area of western Mexico dominated by drug cartels.

One official said a convoy of federal police and soldiers were ambushed near the border of Michoacan and Jalisco states. Neither official could confirm a number of dead. A federal police official said the country's top security officials are en route to assess what happened.

The area between Michoacan and Jalisco is known as a stronghold of the Jalisco New Generation Cartel, which has mounted several large-scale attacks on federal and state forces in recent weeks.

Both sources spoke on condition of anonymity because they were not authorized to speak to the press.