One of the mysterious Apple vans is driving around Hawaii now

There's been a flurry of sightings of mysterious "Apple vans" in recent days. Registered to Apple, the vehicles have a roof-mounted camera rig on them.

This latest photo comes courtesy of Business Insider reader Robert Avallone. He spotted it two days ago on the Queen Ka'ahumanu Highway in Kona, Hawaii, on his way to the airport two days ago.

"We're not used to seeing such cutting edge stuff here on the Big Island," Avallone says.

The vans have also been spotted in New York, Wisconsin, and Panama, according to Apple Insider.

For now, Apple is staying mum on what these vans are for. But some theorise that they could be part of the Cupertino company's rumoured electric car, "Project Titan." The cameras could be part of an experiment in self-driving car technology. Just weeks ago, the idea of an "Apple car" seemed like an outlandish rumour; today, many are taking it as gospel after a flood of leaks.

However, given Apple's culture of extreme secrecy, it's unlikely that Apple employees would so brazenly drive around in vans registered to the company adorned in experimental technology.

The more likely explanation is that they're part of a push to develop street-level mapping for Apple Maps. Apple currently lacks its own equivalent of Google Street View. Apple Insider's Sam Oliver points out that the choice of vehicle - a Dodge Caravan - would be an odd one when developing "futuristic robotics systems." Furthermore, Oliver says, the vehicle's camera appears to have blind spots, a huge no-no for a self-driving vehicle.

That's not to say that Apple isn't developing a car, of course. With new reports of senior hires to lead the project, and the company facing lawsuits for poaching battery manufacturing experts, it's sounding more and more likely. But the Apple vans spotted in the wild are unlikely to be a part of it.