MONTERREY, Mexico: At least 16 people were killed and 30 were injured when a freight train slammed into a packed passenger bus in northeastern Mexico on Friday, authorities said, warning the death toll could rise.

The collision happened when the bus was attempting to cross rail tracks in the city of Anahuac, Nuevo Leon, state civil protection chief Jorge Camacho told AFP.

The accident occurred just after 5pm (2300 GMT) at Camarones station, near the border with the United States.

Two children were among the 16 dead, said Mayor Desiderio Urteaga, although other local officials warned that the final toll could be nearer to at least 20 because some passengers were trapped after the crash.

Images broadcast by local media showed the bus smashed open and split in half by the force of the train.

Nine women and five men were identified among the dead, in addition to the two children, Camacho said.

Of the 30 people injured, 22 were taken to hospitals in the nearby border town of Nuevo Laredo, around 60 kilometres away.

The bus, which normally transports around 40 people, was travelling with 60 passengers, as it made its way from Nuevo Laredo to the northern city of Nueva Rosita.

Camacho said an investigation was underway to determine whether the bus driver was trying to beat the train when the vehicle was struck.

But prosecutors would determine the cause of the accident who was responsible, he added.

There was no fog or rain in the area at the time, he said.

Prosecutors were already at the scene.