The reason is that the oil level has become too high and that oil has spilled over into the engine and there become fuel instead. This could either be because of a software problem in the models, or because too much oil has been added when the car was on service.
If the oil is below the maximum level there is no risk that this will happen. The Volvo-owners concerned have received a letter about this. According to the news agency TT, there are 158,000 such cars in over 30 countries.
About half of the 55 cases have been reported in Germany. None in Sweden. No accidents have been reported in relation to the problem.