SOFIA, April 13 (Xinhua) -- At least six people were killed and 20 others were injured in a bus accident on Friday on the Trakia motorway in Bulgaria, the country's Health Ministry said.

The accident took place around 11:20 a.m. local time near Vakarel, 40 km southeast of Sofia, when the bus overturned off the road, the ministry said.

The cause of the incident are under investigation.

In 2017, car accidents killed 682 people in the Balkan country.