Amazon  has launched its own brand of pet products, called Wag, adding to the internet retailer's expansive list of private-label brands, which has grown to include diapers, clothing and even mid-century furniture.

The Wag brand debuted with dry dog food, with other pet products to be added later. Like some other Amazon private-label brands, Wag products are available to purchase only by Amazon Prime subscribers, who pay an annual fee to free two-day shipping and other benefits, such as access to music, movies and TV shows.

The Wag.com previously resided in Amazon's Quidsi business, which included such specialty retail sites as Diapers.com, Soap.com, BeatyBar.com, Yoyo.com and Casa.com. Amazon bought Quidsi in 2011 for $545 million, but shut it down last year after struggling to make it profitable for seven years.

Amazon launched its first private-label brands in 2009, and now sells items from more than 70 lines, including jewelry, kitchen and health products.

The brand has been in testing for several weeks with members of Amazon's Vine program, which invites trusted reviewers on Amazon to post opinions about new and prerelease products.

The launch of Wag was first reported by Bloomberg.