An initial investigation into the school bus crash that killed a school aide in LaGrange determined the Arlington school district bus failed to stop at a stop sign, collided with a state police patrol vehicle and struck a utility pole, troopers said in a statement on Friday.

The crash that killed the aide, identified as Robin P. Alvarez, 59, of East Fishkill, and injured two students, the bus driver and a state police officer, occurred at around 3:12 p.m. Wednesday at State Route 55 and South Cross Road in LaGrange, state police said.

According to state police, an investigation found the school bus was heading north on South Cross Road, where it failed to stop while attempting to enter State Route 55. The police vehicle, operated by Trooper Christopher Batista, was eastbound on State Route 55 at the time, police said.

Alvarez was not wearing a seat belt, state police said.

This investigation continues.