A 57-year-old man was arrested on suspicion of possession of CS gas and causing a public nuisance after hundreds of people were partially evacuated from Heathrow Airport's Terminal 4 on Monday evening.
Passengers and staff were asked to leave the terminal at about 17:00 BST and were allowed to return around three hours later. Metropolitan Police officers said no hazardous materials were found in the terminal but discovered a can of CS spray that "caused a reaction to those within the airport." The London Ambulance Service treated and discharged 20 people for "irritation." Scotland Yard said the incident is not being treated as terrorism-related and the suspect remains in police custody as an investigation continues.
London Fire Brigade crews attended the scene alongside police and ambulance teams. Heathrow said the terminal reopened to passengers shortly after 20:00 BST and apologised for the disruption, saying it was "very sorry for the disruption caused." Flight tracking data indicated that disruption to flights arriving and departing from Terminal 4 was minimal during the evacuation.
Hundreds of people were reported waiting outside the terminal during the incident while emergency services carried out checks. The Metropolitan Police said officers and specialist units carried out enquiries at the scene and that an investigation is ongoing to establish the full circumstances of the incident.
Police confirmed those treated by ambulance crews were discharged at the scene and there were no reports of serious injuries. Authorities did not provide further details about the suspect's identity or any potential charges beyond the initial reasons for arrest. The Metropolitan Police urged anyone with relevant information to come forward as inquiries continue.
The incident will be subject to further investigation by the police to establish how the CS spray came to be in the terminal and the exact cause of the reported reactions. Heathrow's operations at Terminal 4 have resumed, and airport officials and emergency services continue to review the response to the evening's events.