The commute for thousands of Apple employees just got a whole lot longer.

The tech giant runs shuttle buses full of employees from San Francisco to its headquarters in Cupertino every day, and, according to a source inside the company, someone is attacking those buses — and breaking windows.

On an internal Apple email thread viewed by Mashable, one Apple employee speculated that the culprit may be firing "rubber rounds" at the buses. At least one of the buses only had the outer pane of its double-paned windows broken.

In response, late Tuesday night, Apple emailed employees to alert them that an untold number of shuttles would be rerouted, adding 30 to 45 minutes to riders' commute. Mashable obtained the email and has verified its authenticity.

Here is what the email said:

Subject: Coaches temporarily being rerouted

Due to recent incidents of broken windows along the commute route, specifically on highway 280, we’re re-routing coaches for the time being. This change in routes could mean an additional 30-45 minutes of commute time in each direction for some riders.

As always, the safety of our employees is our first priority. We’re working closely with law enforcement to investigate these incidents and we’ll notify you as soon as the coaches are able to return to the regular route. Thank you for your patience and understanding.

The Apple Commute Team

Image: mashable

Mashable has reached out to both Apple and the local police to confirm whether the shuttles were being shot at, and we will update this when we hear back. At the time of publication, Apple and the local police were not able to confirm what object was shattering the windows. It could, of course, be rocks — but even rocks thrown at a moving vehicle on the highway could result in tragedy.

Officer Art Montiel, of the CHP, confirmed to Mashable that his agency is working with Apple to investigate, and that there have been several reports of an "unknown object" breaking shuttle windows.

Apple confirmed to Mashable that buses are indeed being rerouted, and that it is working with law enforcement to investigate.

While the exact method by which the buses are being attacked remains unclear, that fact that real damage has been done is not. At least four separate shuttles are said to have suffered broken windows while driving on 280.

Image: mashable

According to the source, the incidents occurred on Jan. 12 and Jan. 16. One incident is said to have went down just outside of the city of Woodside, and another outside of Los Altos Hills.

A Google bus was reportedly also attacked.

Anti-shuttle sentiment once loomed large in San Francisco, where activists blamed riders for driving up rents in neighborhoods that included tech-bus routes. A group even took San Francisco to court over the practice in 2014, alleging that the city's pilot program of allowing tech companies to use city bus stops violated state law.

This story has been updated to note that a Google bus was also hit.