The number of pending sales of previously owned homes in the U.S. fell to its lowest level since an industry report began tracking the data since 2001, sign that the housing downturn may not be have reached its lowest point yet.

The National Association of Realtors said its Pending Home sales Index fell 6.5 percent on Tuesday, down from the previous month to 85.5 after an 11 percent drop in July. Economists had expected only a 2.1 percent drop.

The previous low for the index was 89.9 in September 2001. Pending home sales for 2007 are down 21.5 percent from 108.9 a year ago, with all regions reporting lower sales.