Georgia CravenNo trace of any adverse substance has been found after emergency services were called to Heathrow airport, the Metropolitan Police has said.
Terminal 4 was evacuated as fire crews investigated “possible hazardous materials” at the airport.
A source at the Met Police told the BBC the event was partly down to “mass hysteria”.
Heathrow’s spokesperson apologised for the disruption, and said they were working with airlines to ensure flights departed on time.
Junior JonesThe London Fire Brigade said crews were called to the terminal at about 17:00 BST to carry out an assessment of the scene, and Terminal 4 check-in was evacuated as a precaution.
A spokesperson for the airport said it reopened to passengers shortly after 20:00.
About 20 people were assessed by the London Ambulance Service. None was deemed to be in a life-threatening or life-changing condition.
A Heathrow spokesperson said they were “very sorry for the disruption caused”.
Disruption to flights landing and departing from Terminal 4 appeared minimal while the evacuation was under way, according to flight data.
