The collision occurred on the Perote-Xalapa highway near Los Molinos in the eastern state of Veracruz, killing three men, four women and one minor, the Veracruz State Attorney General's Office said.
It added that the Xalapa regional prosecutor's office has opened an investigation to determine the cause of the accident.
According to local media, the ADO bus was traveling the Mexico City-Xalapa route, and it appeared that the bus driver failed to notice the presence of the semi-trailer, leading to the collision.
Veracruz Governor Rocio Nahle said on social media that the state is working in coordination with the federal government to attend to the passengers and families affected by the accident.
This tragic crash came just a day after another traffic accident in the western state of Michoacan, where at least six people lost their lives.
MNA/