The agency said it would complete its review for downgrade within two weeks.
"The sector continues to experience an enormous amount of liquidity pressure. They also face declines in their portfolio market values," Henry Tabe, managing director in Moody's SIV team, told Reuters.
Earlier this week, Citigroup, which faces rising losses from the global credit crisis, said it provided $7.6 billion of financing to SIVs that have had trouble funding themselves recently.
The disclosure, which was revealed in a quarterly filing with regulators late Monday, comes as Citigroup reveals it's named Richard Stuckey to help it untangle the complicated subprime portfolio that may lead to a fourth-quarter loss for the bank.
Citigroup, Bank of America and JP Morgan Chase said in October they would set up a fund, called Master Liquidity Enhancement Conduit, or M-LEC, to help the ailing vehicles, but few details have emerged.
"I'm not aware that any vehicle is sitting on its hands and waiting. On the contrary, people are pursuing individual restructuring proposals," Tabe said.
He said M-LEC could still have a positive impact, and rejected the idea that the two-week review period placed more pressure on the SIVs.
"Our role really is to give investors as accurate a picture as possible of where the rating should be at any point in time. We're not mandated to look at economic, political consequences or any other kind of consequences to our ratings actions," Tabe said.
Moody's said Beta's net asset value had fallen to 75 percent from 87 percent since its last review on Sept. 5. Centauri's fell to 76 percent from 85 percent, Dorada's to 77 percent from 87 percent, Asscher's to 71 percent from 84 percent, and Cullinan's to 69 percent from 78 percent.
"The ongoing liquidity crisis facing SIVs has continued almost unabated since September 5th," Moody's said in its statement.