Shares in local homebuilders tumbled early Tuesday after the National Association of Realtors said pending U.S. home sales in February fell to the lowest reading on record.

The Chicago-based group’s seasonally adjusted index of pending sales for existing homes fell to 84.6, which was 21 percent below last year’s level, the group said in a statement Tuesday. An index reading of 100 is equal to the average level of sales activity in 2001, when the index started.

Shares in Los Angeles-based homebuilder KB Home, which last week reported a first-quarter net loss of $268 million and painted a grim picture for the housing market for the remainder of 2008, saw shares dip 4.6 percent to $26.09 in early trading. Calabasas-based Ryland Group Inc. also saw shares slide 4 percent to $34.66.

However, shares in Ryland and KB had been on a run before today adding 38 percent and 21 percent, respectively, since March 10.