According to a statement by the Los Angeles Fire Department, paramedics believe the child — later identified by the Los Angeles County Coroner’s Office as 10-year-old Janice Xu — suffered cardiac arrest.
“LAFD paramedics responded to a medical aid for a minor female child and furiously worked to save her life,” wrote the LAFD in the statement. “Sadly, all efforts were futile and the child was beyond medical help. Her death was determined on scene.”
Xu was reportedly mid-flight when the medical incident took place, and a team of paramedics met the plane at LAX when it returned for an emergency landing. Officials believe she died on the plane.
Delta released the following statement to PEOPLE: “Delta flight 2423 from Los Angeles to Seattle returned to Los Angeles International Airport shortly after takeoff due to a medical emergency onboard. The flight was met by paramedics.”
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The Los Angeles Police Department will be handling the death investigation, and the LA Coroner will determine the official cause of death, CNN reports. Police do not believe foul play was involved.