One of Google's self-driving cars got into an accident earlier this week. But Google is claiming the auto-pilot-equipped Prius was actually flipped into manual mode when the accident happened, making this a case of user error.

The news initially came from a Jalopnik reader who sent the auto blog a photo of the fender-bender with another Prius near Google's headquarters. The accident appears to be minor and no one was hurt, judging by the photo.

Jalopnik and many other websites reported the incident as the "first caused by Google's self-driving car," which prompted a quick response from a Google spokesperson. In a statement sent to Business Insider, that spokesperson clarified that the car (and Google's software) wasn't to blame for the Prius-on-Prius accident; its driver was.

"Safety is our top priority. One of our goals is to prevent fender-benders like this one, which occurred while a person was manually driving the car," the spokesperson said.

Google's self-driving cars use a combination of video cameras, radar sensors and laser range finders to see other cars and rely on Google Maps and Earth to navigate the road, Google Software Engineer Sebastian Thrun said in October 2010. He also points out that the autonomous cars had trained drivers and software engineers inside during testing.

Naturally if an accident were to occur while the car was in auto-pilot, it could cause some serious problems for Google's project.

Chris Matyszczyk of Cnet has asked Google to release more information on the incident to try to get to the bottom of the situation. Google only offered one additional bit of information, that the car's logs confirmed it was in manual mode.