At least 13 people died and 21 suffered injuries when a bus wheeled out of control in southern Mexico to slam into a rock face, news agency AFP reported quoting authorities.

“The passenger bus left the road and collided with a wall of rock, killing 13 people,” AFP quoted the state prosecutor’s official statement, as saying.

The accident was reported to have occurred before dawn  on a highway in the state of Chiapas near the border with Guatemala.

Initial investigations point to brake failure, according to the authorities, who said that the passengers were mostly residents of communities in the area.