Aug. 27 (Bloomberg) -- Moody's Investors Service is stepping up scrutiny of all prime-jumbo mortgage securities issued in 2006 and 2007 as the surge in U.S. foreclosures spreads beyond subprime loans.

Moody's is studying its rankings on the securities after late payments started increasing more quickly in recent months, according to a statement today from the New York-based ratings company. The bonds aren't all under formal reviews for downgrades, said Thomas Lemmon, a spokesman.

Defaults among homeowners ``across the credit spectrum'' have soared as home prices slump, mortgage rates rise and lenders rein in debt offerings, Moody's said. ``Serious delinquencies'' for prime-jumbo loans in securities rose 72 percent between January and June to 1.7 percent of balances, from 1 percent, according to Moody's.

``In contrast, subprime delinquencies, though much higher, rose 25 percent over the same period, increasing from 25.2 percent to 31.5 percent,'' Peter McNally, a Moody's analyst, wrote in a related report.

Jumbo loans are those too large to be bought or guaranteed by government-chartered Fannie Mae and Freddie Mac, currently $417,000 in most places and up to $729,750 in high-cost areas. Serious delinquencies represent loans at least 60 days late, in foreclosure or already turned into seized property.

Home-Equity Loans

Moody's also projected losses on prime home-equity loans and lines of credit underlying securities. Most of those bonds are insured, the report said.

Losses on prime non-revolving home-equity loans, also called second mortgages, packaged into 2007 bonds will rise to 17 percent on average, the report said. For 2006 bonds, losses will rise to 13 percent, while for 2005 securities they will climb to 6 percent, Moody's said.

For home-equity lines of credit, or HELOCs, in 2007 bonds, losses will rise to 26 percent, Moody's said. Losses on HELOCs in 2006 securities will increase to 24 percent, while losses for 2005 ``vintage'' bonds will reach 9 percent, Moody's said.

To contact the reporter on this story: Jody Shenn in New York at jshenn@bloomberg.net.

Last Updated: August 27, 2008 16:35 EDT