Porsche, the German maker of luxury sports cars, said Wednesday it was recalling 18,165 cabrios worldwide owing to a possible fault in the roof mechanism that could cause the roof to open unintentionally while the car is driving at high speed. The flaw, which could affect Porsche's 993 series cars built between August 1993 and January 1998, had so far not caused any accidents or injuries, the car maker insisted in a statement. The move could affect some 8,252 cars in Europe and 8,952 cars in the United States.