The driver of a 2021 Tesla Model S which caused a serious accident last month involving eight vehicles in San Fransisco, claims that the EV was in full self-driving mode at the time of the crash.

The incident took place at the San Fransisco Bay bridge on Thanksgiving (November 22), but the police report went public this Wednesday. According to California Highway Patrol, the Tesla Model S was cruising at 55 mph (89 km/h) when it suddenly slowed down to 20 mph (32 km/h) while performing a lane change. This dangerous maneuver led to a pile-up, involving eight vehicles. Thankfully there were no casualties but nine people suffered minor injuries including a juvenile that was hospitalized. The crash also caused significant delays on the bridge, closing down two lanes of traffic for around 90 minutes.

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The driver told the police it was a malfunction in Tesla’s full self-driving mode that caused the crash. Officers at the scene couldn’t determine if the FSD function was activated at the time of the accident, but Tesla will be able to recover this information. The police report suggests that in any case, the driver should have taken control of the vehicle in the case of a software malfunction.

This coincides with Tesla’s instructions about the use of its full self-driving mode which is an optional $15k feature for compatible EVs. The FSD became available to all Tesla owners in North America last month, following a limited release for drivers with high safety scores. Despite the name that can be misleading, the automaker warns that it doesn’t make its vehicles fully autonomous, and it “always requires active driver supervision”.

According to Reuters, Tesla and the National Highway Traffic Safety Administration (NHTSA) which usually investigates similar cases did not comment. However, a few days after the crash NHTSA told CNN it was gathering additional information from both the automaker and law enforcement about the incident.

 Tesla Driver Who Caused Eight-Car Pileup Blames Full Self-Driving Mode Malfunction