The National Transportation Safety Board in the United States offered an update on its investigation into the circumstances leading up to a collision on the tarmac at LaGuardia Airport Sunday night that claimed the lives of two Air Canada Jazz pilots.

The plane, with 72 passengers on board, collided with a fire truck shortly after it landed at LaGuardia.

Jennifer Homendy of the NTSB says the fire truck involved did not have a transponder, and it’s not clear if the firefighters, who were responding to another situation and were cleared to cross the runway, heard the command to stop.

“With respect to the truck, did the truck turn, or break? I’ve probably seen the same CCTV video that you have” she told reporters. “We have to do some further investigation on that, including interviews of both firefighters who were on board.”

Canadian officials are working collaboratively with American investigators.

Homendy says there were two controllers in the tower at the time of the collision, and those controllers will be questioned as part of the investigation.

LaGuardia sees some 900 flights a day.