A probe into the 911 system on the day an SUV fatally struck 4-year-old Ariel Russo says human error and not technical problems caused a delay in response time, a city report said Thursday.

Russo was killed June 4 when a driver lost control and slammed into the child and her grandmother at West 97th Street and Amsterdam Avenue at 8:15 a.m.

The Department of Investigation report said a dispatcher, Edna Pringle, at the FDNY's EMS dispatch system never saw the Russo call.

A relief dispatcher filling in for Pringle, who was on break, saw the incident and relayed the message. The first ambulance arrived at almost 8:24 a.m., but Russo died on her way to St. Luke's Hospital.