TEMPE, Ariz. (AP) — Police in a Phoenix suburb say one of Uber’s self-driving vehicles has struck and killed a pedestrian.

Police in the city of Tempe said Monday that the vehicle was in autonomous mode with an operator behind the wheel when the woman walking outside of a crosswalk was hit.

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Sgt. Ronald Elcock says in an email that the accident happened overnight but did not say whether it occurred Sunday night or Monday morning.

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The woman died of her injuries at a hospital and her name was not made public.

Uber has been testing the self-driving vehicles in Tempe and Phoenix for months.

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Uber says on Twitter that it is “fully cooperating” with the investigation and expressed condolences to the family of the victim.