Video footage and audio recordings from air traffic control offered additional insight into the deadly crash at LaGuardia Airport on Sunday.

The National Transportation Safety Board (NTSB) is still investigating the crash, which involved a fire truck and an Air Canada regional jet. On March 24, the board said that the fire truck lacked a device that would have prompted air traffic control to issue a safety alert.

Video footage and audio recordings indicated that the fire truck was responding to concerns about an odor on a separate plane. Around 11:45 p.m. ET, it collided with the Air Canada jet while crossing the runway.

Here is a minute-by-minute breakdown of the incident, which left two dead and dozens injured.

Strange Odor on Separate Flight

United Airlines Flight 2384 left the gate at LaGuardia at roughly 9:20 p.m., but then began circling the tarmac for more than an hour, according to data from FlightRadar24.

During its first takeoff attempt at about 10:40 p.m., the plane reached a ground speed of nearly 110 mph before aborting the takeoff due to a mechanical problem.

The pilots attempted to take off a second time at 11:17 p.m., but were forced to declare an emergency and abort again after flight attendants reported feeling ill and detecting a strange odor throughout the cabin.

Air traffic control audio recordings reveal how the incident played out.

“We have an odor on the plane as well here at this time. We are going to be going back to the gate, request fire as well,” the United pilot said to air traffic control.

The controller responded: “2384, is this odor like a smoke odor … like from a fire?”

“No, it was a weird odor. I don’t know exactly how to describe it. But yeah … we can’t get a hold of anyone at ops for a gate assignment,” the pilot replied.

Air traffic control said no gates were free, but that they would contact the Port Authority for assistance.

United Flight Declares Emergency

At 11:31 p.m., the United pilots escalated the situation and declared an emergency to air traffic control.

“Ground, United 2384 is declaring an emergency. The flight attendants in the back are feeling ill because of the odor. We will need to go into any available gate at this time,” the pilot said.

Air traffic control then offered to direct an emergency vehicle to help evacuate passengers and crew from the plane.

“The fire trucks are over there. They’re going to bring a stair truck just in case you guys do want to evacuate. Let me know if you do,” a controller said.

The United pilot said the crew preferred to wait for a gate.

“But I mean, again, we only got so much time here because there’s still a bit of an odor in the back of the airplane,” the pilot said.

Air traffic control then dispatched emergency vehicles to respond.

2 Vehicles Cleared for Runway 4

Meanwhile, Air Canada Express Flight 8646 began its final approach to LaGuardia en route from Montreal and requested a runway.

“646, number two, clear to land 4,” a controller said at roughly 11:35 p.m.

The emergency vehicle heading toward United 2384 then requested to cross the same runway less than two minutes later, via taxiway D. The controller hesitated, and then cleared the vehicle to cross.

“Truck one and company, cross four Delta,” said air traffic control.

The truck confirmed with the control tower and then began crossing runway 4.

Moments later, a controller realized what was happening and urgently told the truck to stop.

“Stop, stop, stop, stop, Truck 1. Stop, stop, stop. Stop, Truck 1. Stop,” the controller said.

Crash Occurs

At 11:37 p.m., Air Canada Express Flight 8646 collided with the emergency response vehicle while attempting to land. Both pilots died in the crash, and at least 40 people were sent to the hospital with injuries.

Roughly 15 minutes after the collision, a controller was speaking to a Frontier pilot lining up to take off on the same runway.

“That was—that wasn’t good to watch,” the Frontier pilot said.

“Yeah, I know. I was here. I tried to reach out to [inaudible]. We were dealing with an emergency earlier … um, I messed up,” the controller said.

The Frontier pilot responded: “No, man, you did the best you could.”

Transportation Secretary Sean Duffy on Monday said LaGuardia was “very well staffed,” and had 33 certified controllers with more training.

Duffy said the tower aimed to have 37 controllers on staff.

NTSB Still Investigating

The collision is still under investigation, and the NTSB said many questions remain regarding the moments leading up to the point of impact. Investigators are probing why the fire truck crossed the runway while the plane was landing and why it did not stop after the control tower issued last-second warnings.

NTSB Chair Jennifer Homendy said during a press conference on March 24 that investigators still have to review the plane’s cockpit and flight data recorders after authorities recovered them by cutting a hole through the aircraft’s roof.

Homendy also warned against jumping to conclusions about the potential role of air traffic control in the crash.

“I would caution against pointing fingers at controllers and saying distraction was involved. This is a heavy workload environment,” she said.

Homendy said she has seen surveillance footage of the crash, but that investigators still need to speak with the firefighters in the truck to determine if they tried to brake or turn to prevent a collision, or if they even heard the control tower’s frantic warnings.

The Associated Press contributed to this report.