Fifty people are said to have been taken to hospital after a chemical leak spread through Hamburg Airport.
Members of the public were treated for breathing problems and burning eyes by paramedics at the scene.
The German airport is on lockdown amid fears that the leak spread through the air conditioning system, with passengers and crews waiting in the building's car park in temperatures of -4C while the situation is resolved.
All flights were halted for several hours due to the evacuation, airport spokeswoman Karen Stein said to Associated Press. The cause of the incident is currently unknown.
In a series of tweets, Hamburg Airport said: "In central security control, about 50 employees and passengers complained of nausea.
"Rescue workers and airport teams have been taking care of some of the passengers affected. An investigation is currently underway, and we will work closely with the authorities."
"We have cancelled all flight at least until 2pm (1pm GMT) and most parts of the airport have been evacuated," she said.
Local media has also reported the President of Uruguay, who was waiting for a flight, was also affected by the incident, said the Daily Express.
Alarms rang when a nasty "odour" was said to have filled the airport. Flights were halted at 12.20pm due to the fire brigade taking over the terminal building, says the Daily Mail.
Doctors examined patients outside of the building, who were injured by the unknown substance.
According to police at the scene, flights will remain grounded but people have been allowed back into the terminals. Fire crews have also been called to the scene to resolve the scare, as well as several rescue cars.
Hamburg is Germany's fifth-biggest airport, handling 16 million passengers a year.