Alphabet Inc.’s GOOG GOOGL autonomous driving technology unit, Waymo, issued a recall for 444 of its fifth-generation self-driving cars following two collisions with a pickup truck being towed in Phoenix last year.

Incidents in Phoenix: In December, two of Waymo’s autonomous vehicles in Phoenix collided with the same truck, which was being towed backward and slightly occupying two lanes instead of one.

Recall and Software Update: The collisions led to Waymo recalling its self-driving software, a first in the history of autonomous vehicles. The company deployed a software update and rectified all affected vehicles by Jan. 12. These vehicles were in Waymo’s possession and were never sold, according to the U.S. auto safety regulator, the National Highway Traffic Safety Administration (NHTSA).

Compliance and Notification: Waymo submitted a recall report to the NHTSA on Feb. 7 to fulfill relevant notification obligations after multiple discussions with the federal agency.

Significance of the Recall: The incident underscores the heightened scrutiny facing Waymo and other self-driving vehicle operators since its initial deployment.

Public Reaction: In a separate incident last Saturday, a crowd in San Francisco set fire to a Waymo car in the city’s Chinatown district, marking the most destructive attack on a driverless vehicle thus far in the U.S.

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