Terminal 4 at Heathrow Airport has reopened after a fire alarm forced an evacuation on Thursday afternoon (July 6).

The scenes at the airport were described as "chaos" as, according to one journalist and eyewitness, none of the staff members appeared to know what to do in the event of a fire alert.

When asked about the evacuation process by getwestlondon , Harriet Constable said: "Complete mess, I was standing down one end of the terminal when the fire alarm went off, people kind of wandered out of their shops looking a bit confused, and then it emerged very quickly that no one in any of the stores that work here had received any training or information on where they're supposed to direct people in the event of a fire alarm."

The scene inside Terminal 4

She also said she spoke to a Dixons staff member who reportedly said to her: "We are as in the dark as you."

Shortly before 1.30pm, Heathrow Airport posted to Twitter saying it was investigating, the tweet read: “We are investigating this as a matter of urgency and will provide an update shortly. Thank you".

The airport later confirmed an evacuation had taken place, and it is believed the fire alarm first went off at 1.20pm.

Terminal 4 was evacuated following a fire alarm

As the fire alarm was sounding, Ms Constable said she stood around for around 15 minutes, waiting to be told what to do.

She said: "We stood there for about 15 minutes while the alarm was going off and the alarm was saying staff will direct you where to go".

She continued to explain that once a fire door was opened it was "complete chaos as people were trying to get out of this exit".

Heathrow Airport confirmed the reopening of Terminal 4 just after 2pm.

They said: "T4 has now been reopened following an earlier fire alarm evacuation; thank you for your patience as we worked to ensure everyone's safety."

Replying to a tweet complaining of a "horrible evacuation", Heathrow Airport said: "Apologies for the disruption to your journey, Lykle.

"Let us know if you have some suggestions for improvement here at feedback@heathrow.com."

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It appears some passengers were pleased with the evacuation process though, as one Twitter user, @Elise1285, posted saying: "@HeathrowAirport staff were amazing today during T4 fire alarm. #goodhumour #organised #bestofbritish."

Earlier this week, Terminal 3 was evacuated following a fire alarm, which caused flight delays.

To catch up with the events as they happened, head to our live blog .

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