Citing higher-than-expected delinquencies, Moody's Investors Service Inc. last week downgraded $980.1 million of residential mortgage-backed securities issued in 2005 by Bear Stearns Cos.

The securities were made up of adjustable-rate alternative-A mortgages. Such loans were typically given to prime-rated borrowers who did not document their assets and/or income.

Delinquencies on such loans originated from 2005 through 2007 exceed 25% for each year, Standard & Poor's Corp said.

All but one of the 13 tranches of the Bear Stearns deal downgraded by Moody's Friday were cut in February — the other tranche was lowered in November. Two tranches were lowered into junk territory, and six others were already below investment-grade.

This month Moody's has downgraded more than $20 billion of securities backed by jumbo mortgages — those with initial balances of at least $417,000. They have seen surging delinquency rates of late, but they remain far below those of other types of home loans.

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