Funding arrangements for $105 billion of structured investment vehicles (SIVs) were thrown into the spotlight today as Moody's Investors Service extended its high-profile review of the credit-intensive market after receiving "material information" about possible changes.

The rating agency said it had received fresh details about potential operational changes at SIV issuers, which include some of the most powerful international investment banks.

In a short update circulated this afternoon, the agency suggested that a number of investment banks were working with SIV managers, often hedge funds, on bailout strategies for some of their beleaguered vehicles.

Barclays, HSBC and WestLB have already guaranteed to stand behind their SIVs to prevent emergency sales of assets.

Some $60 billion to $65 billion of the SIVS covered by Moody's today represent six SIVs arranged by Citigroup. A spokesman denied any suggestion the Wall Street banking giant was restructuring its SIV exposure, stating that its policy remained one of gradualling reducing its assets.

"In some cases, SIV managers are contemplating changes to their management strategies with the objective of reducing market value risk for senior debt investors, while in other cases SIV managers are in the process of implementing restructuring proposals that would provide more protection to senior debt holders," Moody's said.

Moody's said it needed more time to assess the "evolving nature of these wide ranging remedial measures" and the impact of each individual plan.

The agency said it expected to conclude its SIVs review within two weeks, but would update investors following the conclusion of each individual review.

The move came less than a week after Moody's affirmed, cut or put under review ratings covering about $130 billion of SIV securities, many of which have hit financial crisis after the seizure in credit markets cut off their source of funding.

Moody's has put 42 per cent of the $300 billion SIVs market under review for possible downgrade.

Today's Moody's move came as WestLB, the German banking group, promised to bail out its two SIVs, worth a combined $13.2 billion.

Just weeks after offering an emergency line of credit to its $2.9 billion Kestrel Funding SIV, WestLB agreed within recent days to stand behind its $10.3 billion vehicle, Harrier Finance.

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