Two classes of mortgage pass-through certificates from Structured Asset Securities Corp. series 1998-8 have been downgraded by Fitch Ratings.Class M-1 was downgraded from AA to A-minus, and class M-2 was downgraded from A to BBB-minus. Fitch also affirmed the triple-A rating of class A. The downgrades were attributed to deterioration in the relationship between credit enhancement and expected losses. Fitch explained that the securities are made up of four component classes that support four groups, and each component is backed by a separate mortgage pool. "Although each mortgage group performs differently, since the component bonds are not severable, each component bond reflects the performance of the weakest of all the components," the rating agency said.
