The National Transportation Safety Board has issued a preliminary report on last month's bus crash on I-84 in Orange County.
The bus, transporting students and adults from the Farmingdale School District to a band camp in Pennsylvania, veered off course near Wawayanda.
It crossed lanes and the shoulder before exiting the roadway westbound, eventually colliding with a barrier and coming to a stop at the bottom of a depression.
The driver and two front-row adult occupants were ejected.
Band director Gina Pelletiere and chaperone Beatrice Ferrari lost their lives, while the driver sustained serious injuries.
All 40 high school students taken to hospitals have since been released.
A comprehensive report on the probable cause may take up to a year to complete.
MORE:
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Further coverage on NTSB's investigation