Heathrow Airport live: Terminal reopens after evacuation and 21 people treated by paramedics

London Heathrow is the UK’s busiest airport, and just last month it recorded its busiest day ever.

The airport saw more than a quarter of a million passengers passing through its four terminals – a total of 270,869 passengers – on 1 August.

It came after a month in which it saw almost no growth in passenger numbers, which executives said was due to capacity constraints.

The UK’s busiest airport said that 7,981,137 passengers flew in and out of the terminals in July.

That is compared with 7,980,455 during July 2024.

The incident which closed Heathrow terminal 4 has been stood down, with emergency services confirming the terminal is safe to reopen.

A Heathrow spokesperson said: “Emergency services have confirmed Terminal 4 is safe to reopen and we are doing everything we can to ensure all flights to depart as planned today.

“We are very sorry for the disruption caused, the safety and security of our passengers and colleagues is our number one priority.

“We encourage passengers to check with their airline for the latest information about their flight this evening and our colleagues will be on hand into the night to assist.”

A police source said what happened at Heathrow Airport as a “mass hysteria” type event.

No dangerous substance was found.

A London Ambulance Service spokesperson said a total of 21 patients had been treated, and one had been taken to hospital.

All the others were discharged at the scene.

Around 20 people “reported an injury” and no trace of any “adverse substance” was found after officers were called to Heathrow, the Metropolitan Police say.

A spokesperson said: “On Monday, September 8 at 16:56hrs police were called to a potential hazardous materials incident at Heathrow Airport, Terminal Four.

“Specialist officers attended the scene alongside the London Fire Brigade and London Ambulance Service and conducted a thorough search of the area.

“No trace of any adverse substance was found.

“Around 20 people reported an injury. None were deemed to be life-threatening or life-changing.

Around 20 people have been assessed on scene by paramedics from the London Ambulance Service, London Fire Brigade has said.

The cause of the incident remains under investigation at this time.

Emergency services say Heathrow’s Terminal 4 is safe to reopen, according to airport chiefs.

In a social-media post, the airport said: “Emergency services have confirmed Terminal 4 is safe to reopen and we are doing everything we can to ensure all flights to depart as planned today.

“We are very sorry for the disruption caused, the safety and security of our passengers and colleagues is our number one priority.

“We encourage passengers to check with their airline for the latest information about their flight this evening and our colleagues will be on hand into the night to assist.”

As Terminal 4 reopens, here are the questions that remain about its evacuation:

• What caused the evacuation over a ‘possible hazardous materials incident’?
• How many people were affected – and in what way?
• Will it have an ongoing impact on travel from the terminal this evening?