Shuttle buses carrying Apple and Google employees were hit by unknown objects, possibly rocks or pellet-gun ammunition, on Tuesday.

Four buses carrying Apple employees and one bus carrying Google employees were targeted. The buses suffered broken windows.

No one was injured.

Apple has rerouted some of its buses following the incidents.

Multiple shuttle buses carrying Apple and Google employees were hit by unknown objects in a targeted spree on Tuesday. California Highway Patrol is working with Apple to investigate.

Tech workers travelling to and from work on January 16 were startled when unknown objects – possible rocks or pellet guns, according to the CHP – struck their vehicles and broke windows. The incidents happened in both the morning and evening on both directions of Highway 280, between the cities of Woodside and Cupertino, where Apple is headquartered.

There are at least five reports of shuttle buses hit, with four buses carrying Apple employees and one bus carrying Google employees. No one was injured, the local Fox affiliate, KTVU reported.

A photo of one of the buses provided to Mashable appears in this tweet:

Someone is attacking Apple buses outside of San Francisco https://t.co/DVNkdhnp5v pic.twitter.com/H9rkpMSOzL — FutureShift (@futureshift) January 17, 2018

The tech giants operate free shuttle services between San Francisco and their offices in Silicon Valley, at least an hour’s drive south. The buses are available to employees only, and they have long been a symbol of division between the tech world and everyone else.

The buses are unmarked, so it’s unclear if the attack was targeting Apple.

“This is a serious issue because if this happened to distract the driver – the driver could collide and we could have a multiple vehicle crash at the same time it could cause major injuries to the passengers of the bus and other drivers,” Officer Art Montiel of the CHP told KTVU.

In response on Tuesday night, Apple emailed employees to say that some buses would be rerouted around parts of Highway 280, adding 30 to 45 minutes to their commute.

“As always, the safety of our employees is our first priority. We’re working closely with law enforcement to investigate these incidents,” the email said, according to Mashable.

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