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Twenty-seven people have been treated by paramedics after London City Airport was evacuated because of a "chemical incident".

Hundreds of passengers were forced to flee the airport, at Royal Docks, after fire alarms sounded just before 4.15pm on Friday.

It came after a number of people said they were feeling unwell, although the exact cause is still unknown.

Dramatic images emerged on Twitter of crowds stranded on the runway, while fire engines, police and ambulance crews arrived at the scene.

London Ambulance's assistant director of operations Paul Gibson said: "We were called at 4.11pm to reports of an incident at London City Airport.

"We sent a number of resources to the scene including two single responders in cars, four ambulance crews, an incident response officer and our Hazardous Area Response Team.

"We are treating 26 patients at the scene for difficulty breathing, two patients have been taken to hospital."

One passenger, PR consultant Kim Fletcher, said people were allowed back into the airport at about 7pm.

He said he had arrived at the airport to catch a flight to Hamburg, only to find it closed.

Mr Fletcher added: "There was a woman saying at first she thought she could smell deoderant but it became quite noxious with people coughing.

"I arrived after the airport was shut. Everyone was pushed out across the road.

"There are a lot of cancellations. But there's a sense of people being perfectly patient. There's not been mass hysteria or anything like that."

Boxer David Haye tweeted: "Gutted can’t get to Scotland for @JoshTaylorBoxer fight tonight.

"As #CityAirport got evacuated when everyone started coughing uncontrollably!

Initially it had been reported the airport was closed because of a fire alert.

Chris Daly said: “London City Airport's on fire apparently. All evacuated to the tarmac.”

David Walker added: "No one has a megaphone so it's an airfield of Chinese whispers and confused looking people."

And, James Asser said: "London City Airport seems to be being evacuated.

"Fire engines and lots of flashing lights. Planes stuck just off the runway."

A spokesman for City Airport said after the initial alarm: "The terminal was evacuated after a fire alert was raised in line with normal procedure.

Read more Teenager Tasered and arrested in terror swoop over Tube 'bomb' alert

"It is too early to establish a cause."

A spokeswoman for London Fire Brigade said three fire engines had been sent to the scene.