Heathrow Airport Terminal 4 has reopened after it was declared safe following what emergency services called a "possible hazardous materials incident".
Emergency services were scrambled to London Heathrow Airport shortly before 5pm on Monday and the terminal evacuated and check-in closed.
Elizabeth Line services were unable to call at the terminal’s train station, causing further misery for commuters on a day when the Piccadilly Line, which serves Heathrow’s three Underground stops, is suspended due to the ongoing Tube strike.
Around 20 people were assessed at the scene by paramedics from the London Ambulance Service after reporting injuries.
However, a spokesperson for the Metropolitan Police said "no trace of any adverse substance was found."
"Around twenty people reported an injury. None were deemed to be life-threatening or life-changing. Enquiries are ongoing," a spokesperson for the force said.
The terminal was declared "safe to reopen" shortly after 8pm. Heathrow said “we are doing everything we can to ensure all flights to depart as planned today.”
Follow the latest updates">updates below...
Key Points
- Trains not stopping at Terminal 4
- Watch: Travellers evacuated as emergency services respond
- Passengers should not travel to terminal, airport says
- Heathrow says Terminal 4 'safe to reopen'
- Around 20 people assessed by paramedics
'No trace of any adverse substance found', say Met Police
20:41 , Matt WattsThe Metropolitan Police have released a statement on the incident in which they say ‘no trace of any adverse substance was found’ in their search at Heathrow Airport.
The statement read: “On Monday, 8 September 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 twenty people reported an injury. None were deemed to be life-threatening or life-changing. Enquiries are ongoing.”
Around 20 people assessed by paramedics from the London Ambulance Service
20:35 , Matt WattsMore here from the London Fire Brigade who says that specialist crews were deployed to carry out an assessment of the scene, while the Terminal 4 check-in was "evacuated as a precaution".
Around 20 people have been assessed on scene by paramedics from the London Ambulance Service, the LFB has said.
The cause of the incident remains under investigation at this time, the LFB have said.
Heathrow says Terminal 4 'safe to reopen'
20:26 , Matt WattsA 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.”
LFB in process of standing town from airport
20:04 , Bill BowkettThe London Fire Brigade posted on X, formerly Twitter, that it is in the process of standing down its response to the incident at Terminal 4. The exact cause remains under investigation at this time.
People 'taken ill at Heathrow', say Met
20:02 , Bill BowkettWe are hearing from the Metropolitan Police that a few individuals have been taken ill at Heathrow Airport, although no-one is in a life threatening condition. We will bring you more as we hear it.
Closure causing commuters more insult to injury
19:53 , Bill Bowkett
No trains running to Terminal 4 is causing commuters more insult to injury on a day of mass walkouts.
Services to the airport were already disrupted due to the Tube strikes, with the Piccadilly line serving Heathrow’s three Underground stations suspended.
Heathrow said on Sunday: “London Underground strike action between Sunday, September 7 until Friday, September 12. Tube services will be severely disrupted, with little to no service expected.
“Heathrow Express, Elizabeth Line and bus services are running as normal. Please plan your journey carefully before travelling to the airport.”
People in 'white suits arrived at scene'
19:47 , Bill BowkettA witness who goes by the name of Paul Scott told Sky News that he saw a number of people in white suits arriving at the scene.
Flight delay at Terminal 4 amid evacuation
19:44 , Bill BowkettJust one flight is currently delayed at Terminal 4, according to Heathrow’s departure board: the 10.10pm Saudia service to Jeddah.
Terminal 4 serves 14 million passengers each year
19:39 , Bill BowkettFirst opened in 1986 by His Royal Highness Prince Charles and Princess Diana, Terminal 4 was originally the base for British Airways before they moved to Terminal 5 in 2008;.
It handles approximately 14.2 million passengers each year.
How is the evacuation affecting you?
19:20 , Bill BowkettYou can tell us how the evacuation has affected your flight by emailing bill.bowkett@standard.co.uk.
Watch: Heathrow evacuated as emergency services respond
19:18 , Bill BowkettFootage via @RodleyWhite shows passengers outside the terminal as emergency services deal with an incident at Heathrow T4 security
— Shauns_Aviation🇮🇪✈️ (@Shauns_Aviation) September 8, 2025
The terminal remains evacuated as of now.#Breaking #aviation #Heathrow #Evacuation #London #T4 #Terminal #incident https://t.co/skHkbYYJ87 pic.twitter.com/cVNHlyHeC9
No delays reported thus far
19:15 , Bill BowkettThere are currently no delays or cancellations being reported thus far at Terminal 4, where the incident is taking place.
What is Terminal 4 used for?
19:12 , Bill Bowkett
Heathrow Terminal 4 is used for a variety of long-haul flights by airlines such as KLM, Air France, Etihad, Qatar Airways and Malaysia Airlines.
After a £200 million upgrade completed in 2017, the terminal now features renovated check-in areas, a variety of restaurants and shops and facilities for passengers, including lounges.
Trains not stopping at Heathrow Terminal 4
19:03 , Matt WattsNational Rail has said in a post on X. "Trains are unable to call at Heathrow Terminal 4 due to the emergency services dealing with an incident”.
Terminal 4 closed and passengers should not travel there, Heathrow says
18:59 , Matt WattsHeathrow has released a statement saying Terminal 4 check-in has been closed amid the incident and people are being asked not to travel there.
A spokesperson from Heathrow Airport said in a statement: "Terminal 4 check in has been closed and evacuated while emergency services respond to an incident.
"We are asking passengers not to travel to Terminal 4 and supporting those on site."
The airport says all other terminals are operating as normal and it will provide more information "as soon as we can".
London Fire Brigade 'responding to a possible hazardous materials incident'
18:55 , Matt WattsWelcome to our covarage of an ongoing incident at Heathrow Airport.
London Fire Brigade has released a statment saying: "Firefighters are responding to a possible hazardous materials incident at Heathrow Airport.
"Specialist crews have been deployed to carry out an assessment of the scene, and part of the airport has been evacuated as a precaution whilst firefighters respond.
"The brigade was first called about the incident at 17:01, and crews from Feltham, Heathrow, Wembley and surrounding fire stations have been sent to the scene."
