Sales of existing homes tumbled 8% in September as inventories climbed, highlighting the continued downward spiral of the U.S. housing slump.

The National Association of Realtors said Wednesday that sales of existing homes slid to a seasonally adjusted annual rate of 5.04 million units in September, worse than economists' forecasts for a rate of 5.25 million.

The figures were down 8% from August's downwardly revised pace of 5.48 million homes, and 19.1% below the rate of 6.23 million homes in September 2006.

Lawrence Yun, senior economist at the NAR, said the summer's credit crunch and mortgage mess hit sales for the month.

"Mortgage problems were peaking back in August when many of the September closings were being negotiated, and that slowed sales notably in higher priced areas that rely more on jumbo loans," he said in a statement.

The national median price for an existing home dropped 4.2% from a year earlier to $211,700.

"Because there were fewer transactions at the upper end of the market, there is a downward distortion reflected in a lower national median home price," Yun said. "Home prices continue to trend up in the Northeast and in the condo sector. In other areas not dependent on jumbo loans, such as much of the Midwest, prices are rising."

There were 4.40 million existing homes available for sales at the end of September, a 0.4% increase from August. At the current sales pace, it would take a record 10.5 months to work through that inventory.

Homebuilder stocks were mostly lower. Toll Brothers ( TOL) was down 30 cents, or 1.4%, to $21.34, while Lennar slid 50 cents, or 2.2%, to $21.94. Centex, which reported a big quarterly loss late Tuesday, was down 23 cents, or 0.9%, to $24.41.