GUATEMALA CITY (Reuters) – A collision between a passenger bus and a trailer truck in eastern Guatemala early on Saturday killed at least 20 people, including a 7-year-old boy, doctors and firefighters said.

Guatemalan President-elect Alejandro Giammattei expressed his “profound lament” for the deaths in a post on Twitter.

The accident took place near the town of Gualan, near Guatemala’s Atlantic coast, as the Pullman passenger bus was traveling to the city of Santa Elena, near the border with Mexico.

It was not immediately clear what caused the crash.

Reporting by Jeff Abbott; Editing by David Alire Garcia, Steve Orlofsksy and Sonya Hepinstall