A truck trailer caught fire on the Trakia motorway near Chirpan, at the 185th kilometre heading toward Sofia. The right lane is closed and cars are using only the overtaking lane, the Road Infrastructure Agency said.

The alarm went off at around 11:30 a.m. Two fire crews were sent to the scene and put out the flames, police in Stara Zagora said.

The driver was unhurt and the fire is now under control, police said. Nothing points to the truck hitting another vehicle.

The fire tore through part of the trailer's side frame and burned through its cover, scattering charred cargo across the road. Once the flames were out, firefighters kept working around the truck as a traffic police officer secured the area and directed cars around it.

The road agency urged drivers to take care on this stretch. It's one of the busiest parts of the motorway, carrying heavy truck traffic bound for Sofia from the southern Black Sea coast and the border crossings.

There's no official word yet on what started the fire.