Speculation that Apple is working on a car continues to rumble on, and reports that engine noises have been heard coming from an Apple facility late at night will only fuel the rumours.

A neighbour of Apple's secret Sunnyvale testing facility has evidently reported loud "motor noises" coming from the property on several occasions. The resident found the noise so loud it could be heard even through closed windows, so they decided to write to local officials to complain.

"(Do) there have to (be) motor noises at 11.00 at night like last night?" the resident wrote. "Even with the windows closed I could still hear it."

Apple Insider, which reported the story, connected the dots, stating the company owns seven buildings in the campus based at the Californian city, which underwent renovations last year to include a supposed repair garage and area for auto work.

Some conspiracy theorists believe Apple is working under a different name at the facility. One of the company's leasing a building at the campus, SixtyEight Research, claims to be involved with market research but does not have any information available on its barebones website.

Project Titan being worked on by industry's best?

Sources have revealed shipments related to the development of Apple's car, known as "Project Titan", were delivered to this very campus. However, before we all get too excited, there's no solid evidence of what those "motor noises" actually came from. And, with Apple's involvement with Car Play, it could very well be some sort of testing of its system.

Besides would Apple really be hooning around in a loud, combustion engine car when the industry is leaning towards them rolling out an electric vehicle?

There's no doubt Apple is flirting with the idea of a car, most probably an autonomous electric one, and the company won't be able to hide it for much longer if they are. It is believed hundreds of employees hired from Ford and Mercedes-Benz, recent hires from the world of deep learning, and even someone who specialises in digital number plates and describes himself on LinkedIn as a 'Secret Agent @ Apple Special Projects', are all hints as to what could be in the works.

Apple might want to keep it quiet for now, but these reports of loud, late-night motor noises are getting plenty of people revved up.