A man has been arrested after what emergency services described as a “potential hazardous materials incident” at Heathrow Airport.
The west London airport’s Terminal 4 check-in area was evacuated on Monday, after around 20 people reported injuries.
Specialist officers attended the scene alongside the London Fire Brigade and London Ambulance Service and conducted a thorough search of the area.
Following the search, Metropolitan Police officers located a canister of what is believed to be CS spray.
“It is thought that this substance caused a reaction to those within the airport,” the Metropolitan Police said in a statement.
The force said a 57-year-old man had been arrested on suspicion of possession of a firearm (CS spray) and causing a public nuisance.
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He remains in police custody. The incident is not being treated as terrorism related.
London Ambulance Service said one person had been taken to hospital following the incident.