At least 16 were killed and 30 injured in a collision between a freight train and a bus on a highway in the north of Mexico on Friday evening, an emergency official said.

The bus, ignoring the stop light at a railway crossing, was split in half by the oncoming train, said Jorge Camacho, head of emergency services in Nuevo Leon state.

"We have confirmed the death of 16 people and we believe there are more underneath the bus, so the death toll could reach 20," Camacho said.

A local newspaper said the bus appeared to have been carrying some 60 people, when it only had seating for 40.