The Wall Street Journal is the latest media outlet to claim that Microsoft has made its own smartphone, reporting that the company is working with component suppliers in Asia to test a design.

The WSJ says that the device’s screen measures between four and five inches, putting it in between the iPhone 5 and the Galaxy S III, citing “officials at some of Microsoft’s parts suppliers”.These same officials claim that, while the phone is being tested, it is not certain to go into mass production.

Rumours about a Microsoft smartphone have been rampant for the last four months, after the company unveiled its Surface tablet. The move would give Microsoft more control over the Windows Phone 8 OS and would also reflect CEO Steve Ballmer’s desire for the company to make more hardware.