While driving in autonomous mode, a Google self-driving car was involved in a minor accident with a public transit bus in California on Valentine’s Day, according to an accident report (PDF) filed with the California Department of Motor Vehicles (DMV).

The accident report, signed by Chris Urmson, director of Google’s self-driving car project, says the Google self-driving car was trying to get around some sandbags on a street when its left front struck the bus’ right side. The car was going 2 mph, while the bus was going 15 mph.

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Google said its car’s safety driver thought the bus would yield. No injuries were reported at the scene. Google’s next monthly self-driving car report will be out in a couple days, hopefully Google will address this incident.

The report does not say who was at fault. However, if it’s determined the Google self-driving car was at fault, it would be the first time one of its self-driving cars caused an accident while in autonomous mode.

Update at 3:20 PM ET: Google released a portion of its February self-driving car report early to address the bus crash. Google said the incident is something that happens “every day” on the road. Google also said it “clearly bear[s] some responsibility.” More from Google:

“Our test driver, who had been watching the bus in the mirror, also expected the bus to slow or stop. And we can imagine the bus driver assumed we were going to stay put. Unfortunately, all these assumptions led us to the same spot in the lane at the same time. This type of misunderstanding happens between human drivers on the road every day.

“This is a classic example of the negotiation that’s a normal part of driving – we’re all trying to predict each other’s movements. In this case, we clearly bear some responsibility, because if our car hadn’t moved there wouldn’t have been a collision. That said, our test driver believed the bus was going to slow or stop to allow us to merge into the traffic, and that there would be sufficient space to do that.”

Here’s how the accident report (PDF) describes the accident:

“A Google Lexus-model autonomous vehicle (“Google AV”) was traveling in autonomous mode eastbound on El Camino Real in Mountain View in the far right-hand lane approaching the Castro St. intersection. As the Google AV approached the intersection, it signaled its intent to make a right turn on red onto Castro St. The Google AV then moved to the right-hand side of the lane to pass traffic in the same lane that was stopped at the intersection and proceeding straight.

“However, the Google AV had to come to a stop and go around sandbags positioned around a storm drain that were blocking its path. When the light turned green, traffic in the lane continued past the Google AV. After a few cars had passed, the Google AV began to proceed back into the center of the lane and pass the sandbags. A public transit bus was approaching from behind.

“The Google AV test driver saw the bus approaching the left side mirror but believed the bus would stop or slow to allow the Google AV to continue. Approximately three seconds later, as the Google AV was reentering the center of the lane it made contact with the side of the bus. The Google AV was operating in autonomous mode and traveling less than 2 mph, and the bus was traveling at about 15 mph at the time of contact.

“The Google AV sustained body damage to the left front fender, the left front wheel and one of its driver’s-side sensors. There no injuries reported at the scene.”

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Here is a look at the intersection at which the accident occurred (via Google Maps):

The California DMV said it hoped to speak with Google today for further details of the accident. Robotics Trends has reached out to Google for comment.

Google has been testing two dozen self-driving Lexus SUVs near its Silicon Valley headquarters. Google’s self-driving cars have driven more than 1.3 million miles since 2009. As of January 2016, they had been involved in 17 crashes, all caused by human error.