A bus accident on a motorway in northeastern Germany on Saturday left two people dead and another four seriously injured, police said.

The accident happened on an exit from the A11 motorway that leads to a car park close to an interchange near Prenzlau, north-east of Berlin, German news agency dpa reported. Seven people were slightly injured.

The bus ended up on its side. No other vehicle was believed to be involved and the cause of the accident, which happened in wintry conditions, was not immediately clear. The two people killed were a 29-year-old woman and a 48-year-old man.

Brandenburg state police spokesperson Beate Kardels said the bus operated by Flixbus, Germany’s dominant long-distance bus operator, was heading toward Poland.

The company said it was en route from Berlin to the Polish city of Szczecin, a roughly 150km (93-mile) trip, with 13 passengers and a driver on board.