Nineteen people died and six others were injured when a bus crashed on a highway in Mexico’s central state of Zacatecas on Saturday, local authorities said.

The accident occurred in the early morning hours when the bus carrying the victims collided with the back of a tractor-trailer carrying corn, which had come loose.

Zacatecas Governor David Monreal earlier on Saturday had initially reported a preliminary death toll of 24 people, but the state attorney general’s office later revised the tally in a statement.

The attorney general’s office said it was “carrying out investigations to arrest the driver” of the tractor-trailer.

Efforts were ongoing on Saturday morning to recover some of the bodies that had fallen into a ravine, a local government official who asked not to be named told Reuters.

Video footage showed rescue teams and security forces, including military personnel, securing the area while rescuers worked to recover the bodies.

The bus was headed for Ciudad Juarez, a city on the US-Mexico border in the state of Chihuahua. The victims did not include migrants, according to the attorney general’s office.