BERLIN (REUTERS, AFP) - German authorities on Sunday (Feb 12) closed the airport in the northern city of Hamburg after an unknown substance that caused eye irritation among staff was found in the security check area, a police spokeswoman said.

According to live flight tracking website flightradar24.com some flights were diverted to other airports after the incident.

Firefighters rushed to the airport with multiple vehicles while incoming flights were diverted and hundreds of passengers had to wait outside the terminals in freezing temperatures.

"The airport was completely closed" at around 1130 GMT (7.30pm Singapore time), said Maik Lewerenz of the federal police office at the airport, before it was reopened at 1245 GMT.

"There was an odour problem in the central air traffic control area, where passengers and hand luggage are checked. Some people complained of stinging eyes and coughing," he said, adding that "the cause is unknown so far".

The Bild newspaper reported that an unknown substance was thought to have entered the hall though the air conditioning system, and that fire brigade experts were seeking to identify the substance.