The National Transportation Safety Board has published its preliminary report on last month’s deadly crash involving an Air Canada jet and a fire truck at New York’s LaGuardia airport, concluding communication failures and a lack of transponders in the truck played roles in the collision.

The report, released Thursday, said the truck’s driver heard instructions to “stop, stop, stop” over the radio, but did not realize the message was intended for them.

After the initial warning, the fire truck’s turret operator heard the controller say, “Truck 1, stop, stop, stop,” and realized the warning was for his crew. By then, the report said, the truck was already on Runway 4 as Air Canada Express Flight 8646 was landing.

The jet and the truck collided seconds after the plane touched down. Pilots Mackenzie Gunther and Antoine Forest were killed, and 33 people were injured, including six who had serious injuries.