Is Heathrow Airport open after 21 injured in 'possible hazardous materials' incident?

Travellers flying from Heathrow Airport today may be worrying about whether their flights are going ahead as normal after a serious incident forced the evacuation of Terminal 4 last night. Emergency services, including the Metropolitan Police, London Fire Brigade, and London Ambulance Service, were called to Terminal 4 on Monday evening following reports of a "potential hazardous materials incident." As a precaution, the terminal was evacuated and closed to passengers for several hours.

Around 21 people were treated for injuries during the incident. None of the injuries were life-threatening or life-changing. One person was taken to hospital while others were treated at the scene and discharged.

Despite the alarming nature of the response, no hazardous substance was found following a full search of the area by specialist officers.

A spokesperson from the Met Police said: "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. Enquiries are ongoing."

The London Fire Brigade confirmed it was standing down its response later in the evening, though the exact cause of the incident remains under investigation.

As a result of the incident, thousands were affected and dozens of flights were reportedly delayed.

Terminal 4 is open, and flights are operating as planned today. Heathrow Airport confirmed via social media last night that the terminal had been deemed safe to reopen.

In a post to X (formerly Twitter), the airport wrote last night: "Emergency services have confirmed Terminal 4 is safe to reopen and we are doing everything we can to ensure all flights 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."

Terminal 4 handles flights to European destinations such as Paris, Amsterdam, and Valletta, but also long-haul flights to destinations like Abu Dhabi, Riyadh, Kuala Lumpur, Seoul, Ho Chi Minh City, and more.

The airport has also cautioned passengers that ongoing London Tube strikes may impact travel to the airport, advising travellers to plan their journeys carefully and allow extra time.

Heathrow Airport is not only the busiest airport in the UK, but it is also the busiest in Europe, having recently recorded its busiest-ever day on August 1 2025 with over 270,000 passengers in just 24 hours.