LOS ANGELES - The number of U.S. homes facing foreclosure surged 58 percent in the first six months of the year, the latest sign of growing problems in the mortgage industry, a data firm said Monday.

In all, 573,397 properties across the nation reported some sort of foreclosure activity in the first half of this year, including receiving notices of default, auction sale notices or being repossessed by lenders, Irvine-based RealtyTrac Inc. said.

That was 58 percent higher than in the first six months of 2006 and 32 percent higher than the last six months of 2006.

Among the states with the highest number of homes receiving foreclosure-related notices were California, Florida, Texas and Ohio, the firm said.

RealtyTrac said 925,986 foreclosure filings were sent to homeowners during the first half of the year. Some of those filings targeted the same property, in part because owners had more than one mortgage.

That figure was up 56 percent from the year-ago period and up 39 percent from the last six months of 2006, the firm said.

'We could easily surpass 2 million foreclosure filings by the end of the year, which would represent a year-over-year increase of over 65 percent,' said RealtyTrac Chief Executive Officer James Saccacio.

The national foreclosure rate through June was one filing for every 134 U.S. households, the company said.

In the past, RealtyTrac released the total number of foreclosure notices issued and did not say whether a single property received more than one notice.

The firm now is breaking out the exact property count.