Thousands of passengers had to leave Terminal 2 at Heathrow Airport due to a security alarm.
Footage and videos of the scene showed people calmly leaving the terminal with luggage after reports of a suspicious item were found.
Police presence in the area had increased as travelers evacuated the terminal building.
In a tweet, a witness wrote: “Some sort of security alert at Heathrow Terminal 2 – not sure what was happening at this point, but passengers were moving outside.”
Another person wrote, “Terminal 2 @HeathrowAirport has been evacuated due to a security alert affecting hundreds of passengers.”
However, passengers were now allowed to return to the building and the alarm was set.
A Heathrow spokesman said: “Our teams worked with the police today to respond to reports of a potentially suspicious item in Terminal 2.
“The item has been investigated and does not pose a security risk.
“We would like to thank the passengers, whose journeys were temporarily interrupted, for their patience and can confirm that our operations are now back to normal.”
Many of the world’s largest airlines fly from Terminal 2. These include Air India, SAS and Lufthansa. Some UK domestic flights also use the terminal.