London- London City Airport has reopened after emergency services said there was no evidence of a suspected chemical incident which had prompted the evacuation of 500 passengers.

Paramedics treated 27 and took two people to hospital after the airport was closed and evacuated on Friday afternoon.

The airport was briefly closed as police and firefighters in protective equipment swept the terminal building of the airport with chemical detectors after several people were taken ill, some of them coughing violently.

Later, police said the incident may have been caused by CS gas.

“A search of the airport led to the discovery of what is believed to be a CS gas or spray. Whilst the cause of the incident has not yet been confirmed, officers are investigating if it was the result of an accidental discharge of this canister,” police said in a statement.

“At this early stage, officers are investigating whether it may have been discarded by a passenger prior to check-in. There have been no arrest and inquiries continue,” the statement said.

For his part, David Morris, 28, had been checking in for a BA flight to Edinburgh when he started coughing.

He said: “We were queuing up and we were just about to check our bags in, and I was talking and started to cough to the point I was not able to keep talking.”

“It was getting quite bad and we saw other people starting to cough at the same time. The people behind the desk were coughing the most and quite aggressively.”

“Within two minutes, they shouted for everyone to get out,” he said.

Morris added that whatever was causing people to cough did not smell or have any color to it.

“Everyone was shouting and rushing towards the door,” he added.

The airport later said it had reopened but that flights would be staggered and some disruption was expected.

London City Airport advised people due to fly to check with their airlines for latest flight information.

Incoming planes from destinations such as Frankfurt, Amsterdam, Belfast City and Paris had to be diverted to other airports.

The airport later tweeted: “Airport has now reopened. We thank passengers for their patience, access to terminal will be staggered & disruption to flights expected.”