Google began testing the program last fall and says it now includes 50 online merchants, including O.co, Wayfair and Timbuk2. The program has handled more than 10 million orders, according to Google.

Google is that participation in the program brings merchants more business. For example, it says Timbuk2, a San Francisco company that sells trendy backpacks and messenger bags, improved conversion rates by 2.9 percent and saw average order size increase slightly.

Last week, Google that by the end of the year, its product search results, listed under "Shopping," will be limited to paid advertising. It said this would lead to "better shopping results for users" and "higher quality traffic for merchants."

The company did not immediately respond to a request for comment.

The IDG News Service