The airport said earlier that check-in in its terminal 4 has been closed and evacuated while emergency services respond to the incident.

LONDON, Sept. 8 (Xinhua) -- London Fire Brigade said Monday that they are responding to a "possible hazardous materials incident" at the Heathrow Airport in London.

The airport said earlier that check-in in its terminal 4 has been closed and evacuated while emergency services respond to the incident.

"We will provide further information as soon as we can. All other terminals are operating as normal," it said on X.

Video clips and photos shared online show that large numbers of people have gathered outside the terminal building, with water and blankets being handed out to keep people warm.

"Most of the passengers who were due to board at Terminal 4 have been evacuated away from the building, and many are now waiting outside Terminal 5 along with me," passenger Cao Yuan told Xinhua.■