Banks are bracing themselves for more bad news on their already-pummelled debt after Moody's Investor Services said it was widening its debt review.
Many SIVs invested in sub-prime mortgage debt
On Friday the credit-rating agency said it had either already cut or might cut the ratings of $116bn (£56bn) of debt.
Moody's pointed to the continuing fall in the value of investments made by Structured Investment Vehicles (SIVs),
SIVs, which are affiliated to banks, package debt such as mortgages into bundles and sell them on to investors.
Their value has plummeted since the summer as a result of record levels of mortgage defaults in the US.
Banks worldwide that had bought SIVs based on US sub-prime mortgages suddenly found themselves holding large amounts of debt of questionable value.
Sub-prime mortgages are offered to homebuyers with inferior credit records or low incomes and so present a greater risk for banks.
Many analysts have suggested that the ratings given to SIVs that included sub-prime debt were too favourable.