U.S. home prices are rising, but the rate of increase appears to be slowing down, according to a housing report.

U.S. home prices rose at a slower pace in August than they did in July, according to a survey by S&P Dow Jones.

The home price index ticked up 5.5% in August when compared to the same time last year, but the rate fell from the 5.9% gain in July, according to a Tuesday, Oct. 30, report by The S&P CoreLogic Case-Shiller U.S. National Home Price NSA Index. The home price number is based on a composite of 20 major U.S. cities.

Among the cities with the highest year-over-year gains were Las Vegas, San Francisco and Seattle - with Las Vegas topping the charts at 13.9%. Washington, New York and Chicago all posted gains below 3%.

"Following reports that home sales are flat to down, price gains are beginning to moderate," said David M. Blitzer, chairman of the Index Committee at S&P Dow Jones Indices, in a statement, adding that prices and sales of new single family homes are "weakening" and that high prices and higher mortgage rates may be locking home-seekers out of the market.

For a half year, sales of homes already built fell, and sales of new homes dropped during the past four months, according to a report from the Associated Press.

There's no sign, however, of an imminent housing crisis, said Blitzer.

Shares of major home builders were up, with D.R. Horton (DHI - Get Report)   gaining 2.3%, Lennar Corp. (LEN - Get Report)   rising 3.8%, PulteGroup (PHM - Get Report)  up by 5.2%, NVR (NVR - Get Report)  gaining 2.8%, and Toll Brothers (TOL - Get Report)  advancing by 5.8% in mid-day trading on Tuesday.