Google has said that it bears ‘some responsibility’ after one of its self-driving cars struck a municipal bus in a minor crash in California last month.

The crash has raised concerns with US consumer advocate group Consumer Watchdog and may be the first case of one of Google’s autonomous cars hitting another vehicle and be at fault for the accident. Google said it has updated its software after the crash to avoid future incidents.

In a Feb. 23 report filed with California regulators, Google said the crash took place in Mountain View on Feb. 14 when a self-driving Lexus RX450h sought to get around some sandbags in a wide lane.

Google said in the filing that the autonomous vehicle was traveling at less than 3 kilometers per hour, while the bus was moving at about 24 kilometers per hour.

The vehicle and the test driver ‘believed the bus would slow or allow the Google (autonomous vehicle) to continue,’ the company said.

The Google car, in autonomous mode, reportedly re-entered the centre of the lane, striking the side of the bus and causing damage to the left front bumper, front wheel and a driver-side sensor. The incident report stated that no one was injured in the incident.

Google said in a statement that “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.”

With an investigation underway by Santa Clara Valley’s Transportation Authority, Consumer Watchdog had earlier petitioned the Californian Department of Motor Vehicles (DMV), calling for every ‘robot car’ accident to be investigated by police and accompanied by a release of technical and video data associated with the crash.

A spokesman for the California Department of Motor Vehicles said on Monday it will speak to Google to gather additional information, but added “the DMV is not responsible for determining fault.”