High-tech mystery: Is a Facebook phone in the works?

Facebook could be working on a smartphone, according to paperwork recently spotted by cyber sleuths which the tech giant filed earlier this year.

A Facebook unit devoted to hardware filed a patent application in January for a mysterious "modular electromechanical device" that could have speakers, cameras, microphones, touchscreens, and displays.

"A user can change the functionality of the modular electromechanical device based upon the different functional modules that are connected," read the summary portion of the somewhat cryptic paperwork filed with US patent officials.

Speculation has swirled for years regarding whether the leading social network would try to capitalize on its popularity with is own smartphone.

Facebook has repeatedly dismissed such talk as rumor, and did not respond to an AFP request for comment for this story.

Facebook has a hardware team led by Regina Dugan, a former director of the Defense Advanced Research Projects Agency -- DARPA -- the US agency tasked with identifying and funding breakthrough technologies for national security.

Dugan previously headed advanced technology projects at Google, which dabbled with modular phones in a project call Ara. Google tested Ara but gave up on the project late last year.

Facebook in April launched a mission to sync smartphone cameras' windows with augmented reality, focusing on what people have in hand instead of waiting for high tech eyewear.

While kicking off an annual developers conference in the heart of Silicon Valley, chief executive Mark Zuckerberg called smartphone cameras an initial and promising platform for augmented-reality features in applications tailored to synch with the social network.

"I am confident now we are going to push this augmented-reality platform forward," Zuckerberg said.

"We are going to make the camera the first mainstream augmented-reality platform."

Previously, Facebook had been focused strongly on virtual reality as the next big computing platform, particularly using Rift headgear made by its Oculus unit.