U.S. home prices fell in February for the seventh straight month, a closely followed index released Tuesday shows, with the housing market returning to its lowest levels since the recession began.

Home prices in 20 major U.S. cities declined 1.1 percent in February, according to the Case-Shiller home-price index released by Standard & Poor’s.

Prices rose in one of 20 cities — hard-hit Detroit — in February on a monthly basis. Over the past year, only Washington, D.C., has seen prices advance. Prices fell 3.3 percent year over year in February, compared with a 3.1 percent drop in January.

The 20-city index is slightly above its April 2009 trough, meaning that home prices have retreated almost completely from the gains they posted from May 2009 through June 2010. A drop below the April 2009 level would put housing in a double-dip downturn.

The Coachella Valley’s housing market as a whole will not double-dip, said Patrick Veling, CEO of Real Data Strategies, which analyzes Southern California real estate data. The double-dip nationally will “be based on median price and will be specific to certain submarkets,” he said.

From its peak, the home-price index has dropped 32.5 percent, S&P said. The 20-city index is at 139.27; its low point, in April 2009, was 139.26.

National housing has been plagued by issues that have created a Gordian knot for the sector.

On the supply side, an oversupply of distressed properties is pushing prices down. There are also worries of a so-called shadow inventory of homes that sellers and banks want to list, but are waiting for the right moment to do so.

On the demand side, many consumers still have difficulty qualifying for mortgages, though rates are low.

Economists say a healthy labor market could help cure these ills, but that market has been struggling as well.