Overview

• The check-in area at Terminal 4 was evacuated for about three hours while the London Fire Brigade, Metropolitan Police and London Ambulance Service conducted a precautionary hazmat response.
• National Rail suspended stops at the terminal during the incident and flights faced significant delays before operations resumed later in the evening.
• Police said a 57-year-old man was arrested on suspicion of possession of a firearm (CS spray) and causing a public nuisance after officers recovered a canister believed to contain CS spray.
• Authorities reported no trace of any adverse substance and the fire brigade found no elevated levels of hazardous materials, and the incident is not being treated as terrorism-related.
• Around 21 people were assessed by paramedics and one was taken to hospital, and some accounts suggested a mass-psychogenic element as the cause remains under investigation.