Authorities have detained a suspect at London’s Heathrow Airport following a robbery in a parking garage where pepper spray was used on a crowd, leading to significant travel delays.

Emergency services transported five individuals to a hospital, while 16 others, including a three-year-old child, received on-site medical attention. Officials reported that none of the injuries appeared to be critical.

The chaos erupted in Terminal 3’s garage as a group of four men allegedly snatched a woman’s suitcase inside an elevator, deploying a chemical irritant in the process, according to the Metropolitan Police.

Witness Tom Bate described seeing three young men clad in black, their faces obscured, fleeing from the elevator. Shortly after, he felt a burning sensation in his throat and began coughing uncontrollably.

“Everyone around was coughing,” Bate recounted to 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 UK where most police don’t carry weapons – ran past him shouting.

“It was absolutely terrifying and I 100 per cent 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.