MEXICO CITY (Reuters) -A tractor trailer and a van crashed on a highway in the northern Mexican state of Tamaulipas on Sunday morning, killing 26 people, local authorities said.

The two vehicles crashed about half an hour outside of the state capital Ciudad Victoria and then caught on fire, the Tamaulipas' public security ministry said.

Once authorities arrived at the site of the crash, they found the truck carrying the trailer was no longer at the scene.

A source at the Tamaulipas prosecutors' office said investigators were unsure whether the driver of the truck had fled or if he was also killed in the crash.

The passengers of the van, believed to be from a private transportation business, included children, the source said.

The victims are all thought to be Mexicans as national IDs have been recovered from the scene, the source said.

(Reporting by Kylie Madry; Editing by Chris Reese and Tom Hogue)