An Air Canada regional jet collided with a fire truck while landing at New York’s LaGuardia Airport late Sunday, killing the pilots and injuring several others, officials said. The impact severed the cockpit, and a flight attendant who was still secured to her seat was thrown away from the immediate crash site, her daughter told a Canadian TV station. Airport officials said the fire truck had been crossing the tarmac just before midnight after it was given permission to check on another plane that had aborted its takeoff.

Port Authority of New York and New Jersey officials said the two people in the fire truck were Sgt. Michael Orsillo and Officer Adrian Baez, and that their injuries were not believed to be life-threatening. Port Authority executive director Kathryn Garcia said one of the fire truck crew was expected to be released Monday while the other would remain in the hospital for observation. Garcia also said the pilot and copilot who died were both based out of Canada, and that LaGuardia had its first fatal crash in 34 years.

The NTSB is leading the investigation, and officials said Canada has also sent a team of investigators. NTSB chair Jennifer Homendy said the runway where the crash happened is likely to be closed for “days” as investigators sift through a “tremendous amount of debris.” Homendy said authorities recovered the plane’s cockpit and flight data recorders and sent them to the NTSB’s lab in Washington, describing that workers had to cut a hole in the aircraft’s roof to reach the recorders because its tail was on the ground; Homendy said the cockpit voice recorder was not damaged. She also said it was too early to answer many questions and that more information is expected to be released Tuesday.

Officials and aviation-safety figures said the focus is on whether air traffic and ground traffic were properly coordinated as the plane was landing. Mary Schiavo, a former Department of Transportation inspector general, said “This has been happening for years and sadly some of the most horrific air crashes in history happen on the ground at the airport.” Transportation Secretary Sean Duffy said LaGuardia is “well-staffed” but faces a shortage of controllers, with 33 certified controllers and a goal of 37; he said more than one controller was on duty at the time of the accident. Former FAA air traffic control chief Mike McCormick said air traffic controllers are generally not affected by the partial government shutdown because it does not affect the controller workforce, but he suggested the overnight tower shift at the time of the crash may have been lightly staffed.

Audio from airport communications and accounts from witnesses were among details emerging as investigators worked. The AP reported that in the radio transmission recorded around the time of the crash, an air traffic controller could be heard urging the fire truck to stop, saying “Stop, stop, stop, Truck 1. Stop, stop, stop,” and then “Stop, Truck 1.” A person familiar with the investigation also said on anonymity grounds that a security camera video showing emergency vehicles moving across the tarmac minutes before the landing was authentic; the recording shows the lead vehicle continuing into the path of the aircraft.

Homendy said authorities recovered key flight instruments for analysis, and she gave additional detail on what investigators are handling at the crash site. Photos and video shared online showed cables and debris hanging from the mangled cockpit, and the fire truck flipped onto its side with damage centered on its back half. The airline said the flight was operated by Jazz Aviation on behalf of Air Canada and originated at Montreal-Pierre Elliott Trudeau International Airport, with the plane’s remains still on the runway several hours after the crash.

Witness accounts also described the moments immediately after the collision. Flight attendant Solange Tremblay suffered multiple fractures to one leg and would need surgery after being thrown from the plane, her daughter Sarah Lépine told TVA Nouvelles, calling her survival “a total miracle.” Passenger Rebecca Liquori told News12 Long Island that she felt the plane brake hard after hearing a loud boom and that people hit their heads and were bleeding, adding that passengers helped each other slide down a wing. Clément Lelièvre said the pilots’ “incredible reflexes” helped save him and others, describing that the pilots braked extremely hard just as the aircraft touched down.

After the crash, LaGuardia shut down during a period of broader travel disruption, and flights later resumed with lengthy delays. The crash shut down the airport during what AP reported was already a messy time at U.S. airports because of a partial government shutdown, which affected security checkpoints at other airports. Garcia said the airport has a system designed to help keep track of planes and vehicles crossing the airport, and McCormick said an alarm heard in the background of the air traffic control audio was likely linked to that system and would have alerted the tower to a potential collision, while also noting the system does not determine whether a vehicle has clearance to cross a runway.

Investigators and officials said additional information will be released as the NTSB reviews the recorders and examines coordination of runway access and landing sequencing. Homendy said it was too early to answer key questions, and that the agency expected to provide more details Tuesday as the inquiry proceeds.