Thirty-eight people died in a weekend road accident in Mexico as a truck collided head-on with a bus, authorities said Tuesday in the first official toll from the tragedy.

It happened Saturday in the southeastern state of Campeche and the fatalities were 36 people in the bus and two in the truck, said Jackson Villacis, a state prosecutor.

Villacis said relatives of victims claimed there were four additional fatalities but these bodies have not been found.

This is the first official toll from the accident in the Yucatan peninsula in which the truck swerved into the lane of the oncoming bus.

Both vehicles caught fire and burned down to charred ruins.

Over the weekend reports said there were dozens of deaths but there was no official figure.

Nine people survived the accident.

The bus had set out Saturday from Tabasco state and was headed for the Caribbean beach resort city of Cancun.

Footage posted on social media showed the truck and the bus engulfed in flames as people screamed for help.

Road accidents in Mexico involving big rig trucks have risen in recent years due to poor vehicle maintenance and drivers who are either reckless or overworked.

In another horrific accident, 54 people died Monday in Guatemala when a bus crashed through a guard rail and plunged into a ravine, officials said, lowering an earlier death toll by one fatality.