A polcie spokesman confirmed a suspicious gas or toxin was found during a security check.
Unconfirmed reports have suggested the suspect gas could have streamed into the airport through the air-conditioning system.
The alarm was raised late this morning after several people reported smelling nasty odours and complaining of having breathing problems, severe coughing and burning eyes.
Emergency services rushed to the scene
Fire crews rushed to the scene along with several rescue cars and extinguishers.
Rescue services quickly evacuated the airport between terminals one and two – sending hundreds of passengers and employees to wait in the opposite parking area in sub-zero temperatures to keep the access roads clear.
All flights were initially diverted and grounded – and according to live flight tracking website flightradar24.com some flights were diverted to other airports after the incident.
Airport spokeswoman Karen Stein said: “We have cancelled all flight at least until 2 p.m. (1300GMT) and most parts of …