In an effort to build on the success of the popular Kindle Fire and better compete in an already crowded tablet market, Amazon is now reportedly working on "up to five or six tablets" in different sizes. The line would include a 10-inch tablet that could rival Apple's iPad, said the president of U.S. retail chain Staples.

Staples retail head Demos Parneros told Reuters that Amazon is working on several slates of varying sizes, but did not detail when the tablets would arrive or even if the testing prototypes would actually see the market. While Parneros did not offer a lot of information to go on, it would make sense for Amazon to expand and diversify its tablet line.

Amazon's 7-inch Kindle Fire introduced last October proved to be a decent success, but sales have started to decline. Competition from Google's recently launched Nexus 7 is likely to hurt Amazon's position in the tablet market even further, as it comes in the same price range but offers more hardware features, including a camera.

With a new range of tablets varying in size and features Amazon could stay competitive and keep an upper hand in the tablet race, provided it can continue to offer the devices at a low price point. The new tablets would build on the success of the Kindle Fire and would likely draw a nice profit for the company, especially if Amazon throws in more exciting features to entice consumers.

Meanwhile, Geek.com also listed two possibilities on what the five or six new SKUs (stock-keeping units) will be. "One is that Amazon will offer both a seven and 10-inch Kindle Fire and that there will be multiple storage capacities offered - say 16, 32, and 64GB," wrote the site. "That would cover six SKUs. Another is that Amazon is only going to offer up an updated 7-inch Kindle Fire, but that there will be a 3G-capable version. Again, roll in multiple storage capacities and you've got six SKUs."

GottaBeMobile also took a shot at predicting how the Kindle Fire lineup might unfold. According to the site, Amazon may introduce a 7-inch Kindle Fire 2 in 8GB and 16GB storage configurations, a 10-inch Kindle Fire 2 in 16GB and 32GB versions, and a 10-inch 4G LTE Kindle Fire 2, also in 16GB and 32GB configurations.

Other reports indicate that Amazon will also introduce a Kindle Fire 2 model with 4G LTE connectivity. That model will reportedly sport the same 7-inch display, but with an upgraded 1,280 x 800 pixels resolution. Lastly, TechNewsaurus reported that Amazon will make a formal announcement on July 31, and the Kindle Fire 2 will launch on Aug. 7.