A 57-year-old man was arrested on suspicion of possession of a firearm (CS spray) and causing a public nuisance after a "potential hazardous materials incident" at London’s Heathrow Airport that left about 20 people with irritation and forced the temporary closure of Terminal 4, police said.
Metropolitan Police said officers were called on Monday, Sept. 8, at 16:56 BST to reports of a possible hazardous substance in Terminal 4. Specialist officers attended alongside the London Fire Brigade and the London Ambulance Service and conducted a search of the terminal.
Following the search, the Met said officers located a canister believed to contain CS spray. "It is thought that this substance caused a reaction to those within the airport," the force said. Around 20 people reported to paramedics with irritation symptoms and one person required hospital treatment; the force said there were no life-changing or life-threatening injuries.
Police said the incident is not being treated as terrorism-related. The arrested man remains in police custody, the Met said on Tuesday, Sept. 9.
Emergency services evacuated and closed the terminal for roughly three hours during the response, a period that led to delays and disruption for thousands of passengers. Footage and photographs from the scene showed emergency crews in white protective suits entering the building while staff handed out water and emergency foil blankets to people waiting outside.
A Heathrow Airport spokesperson said emergency services had "confirmed Terminal 4 is safe to reopen" and that airport staff were working to get flights departing as planned. "We are very sorry for the disruption caused, the safety and security of our passengers and colleagues is our number one priority," the spokesperson added, urging passengers to check with their airlines for the latest flight information.
Police and emergency services conducted a thorough search of the area before reopening the terminal, the Met said. Officers continue to review CCTV and other evidence as part of the investigation into the possession and use of the spray and the circumstances surrounding the incident.
Witnesses described scenes of confusion and distress as passengers and staff evacuated. The London Ambulance Service attended and treated multiple people at the scene; the force’s involvement formed part of the coordinated emergency response alongside the Met and the fire brigade.
Officials have not given details about any motive, how the substance was deployed, or whether further arrests are expected. The Met reiterated its assessment that there is no indication the incident is linked to wider hostile activity.
Heathrow — one of the world’s busiest airports — has faced occasional security incidents in recent years; airport and policing authorities said swift multiagency action in this case prevented more serious harm. The airport said staff would remain on hand into the night to assist affected passengers, and airlines were managing disrupted schedules following the closure.
The Met’s investigation is ongoing and officers asked anyone with information or footage of the incident to contact police.