Alphabet Inc's (GOOG  ) (GOOGL  ) Google Waymo is recalling about 672 of its self-driving vehicles after identifying their inability to avoid a pole or pole-like objects.

What Happened: The company identified the issue after one of its self-driving cars collided with a wooden utility pole in an alleyway in Phoenix, Arizona late last month, is said in a filing with U.S. auto safety regulator National Highway Traffic Safety Administration (NHTSA). The car was executing a low-speed pullover maneuver when the collision happened.

While there were no passengers in the vehicle and no injuries pertaining to the collision, the company said the vehicle bore some damage and alerted Waymo to its software's inability to avoid poles.

The company fixed the issue by June 6 with a software update to improve its reaction to pole-like objects and "robust" mapping updates and improvements.

Why It Matters: In May, NHTSA commenced a probe into Waymo vehicles following reports of unexpected driving behaviors. These reports included collisions with stationary and semi-stationery objects such as gates and chains, as well as collisions with other parked vehicles. Some instances also pertain to the driving system disobeying traffic rules.

The regulator expressed concern that these driving behaviors may increase the risks of crash and injury. "Although this office is unaware of injury allegations, several of the incidents involved collisions with clearly visible objects that a competent driver would be expected to avoid," the regulator wrote in a letter to Waymo dated May 23.

Waymo currently operates robotaxis in parts of San Francisco, Los Angeles, and Phoenix. The company intends to expand services to Austin soon.