Over 20 people treated after ‘mass hysteria’ incident at London’s Heathrow Airport

More than 20 people were treated by paramedics and one was taken to hospital after an incident at Heathrow Airport’s Terminal 4 that police later described as a “mass hysteria” type event, according to officials and media reports.

The alarm was raised at about 4:50 p.m. on Monday when emergency services were called to reports of a possible hazardous materials incident. The London Fire Brigade said specialist crews evacuated the Terminal 4 check-in area as a precaution while carrying out an assessment.

The London Ambulance Service said 21 patients were treated at the scene, with all but one discharged. The person taken to hospital was not believed to be in life-threatening condition, and the nature of the injuries was not disclosed.

A source at the Metropolitan Police told the BBC that no hazardous material was found and the incident appeared to be a “mass hysteria” type event that had “snowballed.” The circumstances remain under investigation.

Heathrow Airport said Terminal 4 has been declared safe and reopened, apologizing to passengers for the disruption. “We are doing everything we can to ensure all flights depart as planned today,” the airport said in a statement.

The airport, located in west London, is one of the busiest airports in the world and the main international gateway to the United Kingdom.