Integrated Asset Services, LLC (IAS) said Tuesday that its benchmark for national house prices fell 0.6 percent in February. The drop marked the seventh straight monthly decline reported by the collateral valuation firm and pushed its home price gauge to April 2004 levels.

With the February decline, the IAS360 House Price Index is down 7.5 percent from July 2009 and 25 percent from July 2007, the index’s high-water mark. February’s closing level is only fractionally higher than the index’s closing value six years ago, IAS said.

Two of the four U.S. census regions did manage modest gains in February – the Midwest, with a 0.8 percent rise, and the Northeast, with a slight 0.2 percent improvement. But IAS says the increases were weaker than usual for the time of the season.

For their part, the South and West regions actually lost ground across what is normally a positive period, the South falling another 1.4 percent, and the West slipping 0.9 percent. Both regions have produced negative returns for seven straight months.

“By now, the normal seasonal upturn in housing activity should have begun,” said Dave McCarthy, president and CEO of Integrated Asset Services. “But we’re looking at trend lines for neighborhoods all around the country and we just aren’t seeing the typical forces at work.”

Results in a number of the nation’s large metropolitan statistical areas seemed to confirm the point. The Los Angeles metro, for example, posted a 1.4 percent decline in home prices for February and doesn’t appear to be following the seasonal pattern this year, most likely due to the extreme economic crisis in California, IAS said.

Other major metro areas, including Las Vegas, Miami, and Washington D.C. are also running counter to the typical seasonal upswing. Home values in Las Vegas lost 1.0 percent from January to February. Miami prices dropped 2.0 percent, and the nation’s Capitol dipped 0.9 percent.

Analysts believe one reason home values are under pressure is that foreclosed homes are adding to the inventory of unsold properties, which compete with more expensive new housing. According to the latest published figures, more than 300,000 homes received foreclosure filings last month, and the number may reach 4.5 million by year-end.

“Residential real estate markets are a local phenomenon and easily influenced by numerous market factors,” McCarthy explained. “A keen understanding of what’s going on at the local level is going to be absolutely critical as we move through what is arguably the most volatile time in the history of the U.S. housing market.”