At least 12 people died when a bus and a car collided in a mountainous part of the eastern Mexican state of Veracruz, local emergency services said.
The accident near the town of Naolinco sent the bus tumbling down a slope some 200-300 metres, and left at least 15 passengers injured, a local official said.
Emergency services believe there were 27 people travelling on board the bus, the official added.
The crash occurred at a bend in the road in foggy conditions, and preliminary evidence suggested the driver of the car that hit the bus fled the scene, he said.
Lethal traffic accidents are common on Mexican roads, claiming hundreds of lives a year. Last April at least 43 people were killed when a cargo truck hit a bus in Veracruz state.