Firefighters and an airline official have been taken to hospital after a fire broke out at Luton Airport on Tuesday.
Five people have been admitted to Luton and Dunstable hospitals for smoke inhalation.
A sixth person was treated at the scene but did not require further medical treatment.
All flights at London Luton Airport were suspended shortly after the fire broke out at around 9pm.
Luton Airport has since confirmed flights will remain suspended until noon on Wednesday.
The building has partially collapsed, Bedfordshire Fire and Rescue Service confirmed.
Footage posted on social media showed flames and smoke tearing through cars parked at the airport terminal on Tuesday evening.
Vehicle alarms and loud explosions could be heard, with one witness saying the speed in which the blaze tore through the upper floor of the car park was “incredible”.
One witness said on X, formerly known as Twitter, that it looked as though the whole car park had collapsed, while another said vehicles in the car park were exploding every few seconds.
The airport said on X: “All flights are currently suspended as emergency services respond to a fire in Terminal Car Park 2.
“Access to the airport is currently restricted and we ask that people do not travel to the airport at this time.
“Additional staff are on hand to provide assistance to passengers.”
“Passengers should stay in touch with their airline for further flight information.”
It is unknown if any passengers are trapped on the tarmac, inside the airport or in the Terminal 2 car park.
Bedfordshire Fire and Rescue, Bedfordshire Police and the East of England Ambulance remain on the scene.
Passengers on flights out of Luton have been asked to remain away from the area.
People living nearby have been advised to steer clear and keep their windows closed to reduce health risks.
Russell Taylor, 41, an account director from Kinross in Scotland, saw the flames after flying in to Luton Airport from Edinburgh.
He told the PA news agency: “There were a couple of fire engines with a car ablaze on the upper floor of the car park at just after 9pm.
“A few minutes later most of the upper floor was alight, car alarms were going off with loud explosions from cars going up in flames.
“The speed in which the fire took hold was incredible.”
The East of England Ambulance said paramedics have taken five people suffering from smoke inhalation to hospital for treatment.
The airport’s website says the car park that is on fire is new.
“Our brand new multi-story car park offering secure, on-site parking using just a five-minute walk to the terminal entrance,” the website says.
Andrew McCullough from County Antrim, Ireland, was one of many travelers who had their travel plans hit.
Tweeting from the tarmac, Mr McCullough wrote: “[The captain on this easyJet flight that has been] waiting to take off [now] has said the airport is closed.”
“We [were] unboarded from the plane.
“My flight had boarded when the airport was closed [due to the fire]. We were then unboarded and waited [for] maybe an hour before the flight was cancelled.
“Staff dealt with it all very well.”