An evacuation of a Heathrow Airport terminal over a mystery chemical incident which left 21 people needing medical treatment was caused by 'mass hysteria'.
A 'possible hazardous materials incident' saw Terminal 4 shut for around three hours shortly after 5pm on Monday, forcing crowds of people to gather outside with their luggage while ambulances and fire crews rushed to the scene.
Twenty-one people were assessed by paramedics at the airport, while one person was taken to hospital, amid fears of a chemical leak.
However, police confirmed that 'no trace of any adverse substance was found' at the airport, while emergency services stood down their response at around 8:30pm.
'Around 20 people reported an injury. None were deemed to be life-threatening or life-changing. Enquiries are ongoing,' a spokesperson for the Metropolitan Police said.
