DETROIT (AP) — General Motors' Cruise autonomous vehicle unit has recalled 300 robotaxis to update software after one of them rear-ended a municipal bus in San Francisco.

Cruise says in government documents posted Friday that the robotaxi inaccurately predicted how the bus would move as it pulled out of a bus stop on March 23. The "articulated" two-section bus slowed as it was leaving the stop and was hit by the self-driving vehicle.

It wasn't clear from the documents if anyone was hurt. Cruise said in documents sent to the National Highway Traffic Safety Administration that it did the software update on March 25.

"Cruise determined that the collision was caused by an issue related to prediction of the unique movements of articulated vehicles in rare circumstances," the company said in documents.

The company said no other crashes have happened due to the problem and that the same thing won't happen again after the update. Cruise said it did the recall to be transparent and add to public understanding of the crash.