All flights at London Luton Airport have been suspended and people have been asked not to travel there because of a large fire in a terminal car park.
The Terminal Car Park 2 suffered “a significant structural collapse”, Bedfordshire Fire Service says.
Fifteen fire engines attended the blaze which affected half of the multi-storey structure and involved numerous cars.
Flights have been suspended until 12:00 BST on Wednesday for the safety of passengers and staff, the airport says.
Four firefighters and a member of airport staff were taken to hospital after an earlier report of smoke inhalation, while another patient was discharged at the scene.
Hundreds of people are stranded in Luton this morning, with no way of getting home.
Many told the BBC that their cars were in the car park.
All the hotels are fully booked and many passengers claim the airlines have simply dumped them.
There is a heavy police presence with many officers trying their best to direct people away from the scene. For some stranded passengers, English is not their first language.
Many are scrambling with their luggage to Luton Airport’s train station in a bid to catch a train or coach to other airports in order to catch flights in the next few hours.
London Luton Airport is the UK’s fifth largest airport after Heathrow, Gatwick, Manchester and Stansted, carrying more than 13 million passengers in 2022.
The ambulance service said a critical incident had been stood down but it would “remain on scene to support fire and rescue colleagues”.
Footage shared online shows huge flames and billowing smoke from the top floor of the building.
Earlier, the ambulance service said a member of the public and six firefighters had suffered smoke inhalation.
The airport said a car fire had spread.
Vehicle alarms and loud explosions could be heard, with one witness describing the speed at which the blaze had torn through the upper floor of the car park as “incredible”.
A passenger who was on board a plane that was due to take off as the fire broke out said: “We were all just told to get off the flight, that there was an incident and then we were left in the airport with no proper explanation.”
Two hours later, they were told there was a major incident and that they would need to leave the airport.
“It was all a little bit confusing because I don’t think the staff knew exactly what they were supposed to be doing.”
Another passenger said “some of us were very frightened because we’d travelled by ourselves” and “didn’t have anywhere to go” after being told to leave the airport.
Russell Taylor, 41, an account director from Kinross, saw the flames after flying in to London Luton 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 fire service said the first call about the fire had come at 20:47 BST.
It added: “Fire crews are working to extinguish the fire and prevent it from spreading to adjacent buildings and vehicles on air side of the airport.”
Police and ambulance are in attendance and the fire service advised local residents to close windows and doors and avoid the area.
The airport said in a statement: “All flights are currently suspended as emergency services respond to a car fire that has spread 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. Further updates to follow.”
It said additional staff were on hand to provide assistance to passengers, and said they should contact their airline for flight information.
The airport’s website says the car park that went on fire is located “just a five-minute walk to the terminal entrance”.