LONDON (AP) — Thousands of travelers faced disruption as all flights were suspended on Wednesday at London’s Luton airport after a fire tore through a newly built parking garage, destroying vehicles and partially collapsing the structure.

Four firefighters and an airport employee were treated in hospitals for smoke inhalation after the fire, which erupted on Tuesday evening.

All flights were suspended until at least 3 p.m. on Wednesday, the airport said in a statement, and would-be passengers were asked to stay away because emergency crews were still on the scene.

Luton, about 56 kilometers (35 miles) north of central London, is a hub for easyJet, Ryanair and other budget airlines running flights to destinations in the United Kingdom and Europe.

Some passengers had to wait at the nearby railway station because the airport was closed.

Nikodem Lesiak, a university student trying to return to Poland, said he had spent the night at the station.

“When we got here, we found out Luton is burning and everything is closed, and we were supposed to have our flight at 7:50 today but it was cancelled,” he said.

Video posted on social media and on the websites of British news outlets showed police and fire department vehicles gathered outside a multi-story parking structure where the top level was engulfed in flames. The parking garage for Terminal 2 partially collapsed.

In addition to the five people hospitalized, a sixth person was treated at the scene.

Bedfordshire Fire and Rescue Service said its crews were “monitoring the smoldering remains” on Wednesday morning. Chief fire officer Andrew Hopkinson said the blaze is thought to have started with a diesel vehicle, and the recently opened parking garage did not have sprinklers.

Authorities said they don’t believe the blaze was started intentionally.

Russell Taylor, 41, an account director from Kinross in Scotland, saw the flames after flying in to Luton from Edinburgh. He told the PA news agency that he first saw a couple of fire engines with a car on fire on an upper level.

“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,” he said. “The speed in which the fire took hold was incredible.”