U.S. home foreclosures in May totaled 176,137, up 19 percent from April, reflecting a poor spring housing season and foreshadowing even higher levels later in 2007, real estate data firm RealtyTrac said on Tuesday.

The latest figure -- a sum of default notices, auction sale notices and bank repossessions -- was 90 percent higher than a year ago, RealtyTrac said in its May 2007 U.S. Foreclosure Market Report.

RealtyTrac said there was a national foreclosure rate of one foreclosure filing for every 656 U.S. households during May.

The default rates in the subprime segment of the U.S. mortgage market, which caters to borrowers with poor credit histories, have jumped in recent months as the housing industry has slowed and prices have fallen.

More than two dozen lenders in the subprime mortgage sector have collapsed as rising defaults drove them out of business during a downturn in the housing market.

Market observers are keeping a watchful eye on the subprime crisis because it has triggered broader concerns that the fallout may spread to mainstream lenders and damage the economy.