LONDON (AP) — Police arrested a man at London's Heathrow Airport on Sunday after a crowd of people were hit with pepper spray during a robbery at a parking garage that caused several hours of travel disruptions.

Five people were taken by ambulance to a hospital and another 16, including a 3-year-old girl, were treated at the scene, officials said. None of the injuries was believed to be serious.

The incident in the Terminal 3 garage on the outskirts of London happened when a group of four men stole a woman's suitcase in an elevator and sprayed her with an irritant, Metropolitan Police said.

Passenger Tom Bate said he saw three young men in black with their heads covered run from the elevator and then he experienced a burning sensation in his throat and immediately began hacking.

“Everyone in the room was coughing," he told Sky News. “It was one of the weirdest things I’ve ever experienced.”

Police said the robbery victim and the assailants knew each other and the crime was not being investigated as terrorism.

Bate said he initially feared the worst as a large group of officers carrying guns — a rarity in the U.K. where most police don't carry weapons — ran past him shouting.

“It was absolutely terrifying and I 100% believed that I was in a terrorist attack for a few moments,” he said.

He said an officer pointed a gun at a man and ordered him to the ground to arrest him.

A 31-year-old man was held on suspicion of assault. Police were searching for the other suspects who left the scene.

The incident caused several hours of delays for passengers trying to get to and from the airport.