The airport in Germany's third largest city was temporarily shut down and evacuated early Sunday afternoon. 

Hundreds of travelers were forced to wait outside the airport in freezing temperatures after a discharge of a corrosive substance caused eye irritation and breathing difficulties among people in the security check area, a police spokeswoman said. 

More than 50 people, both passengers and staff, had complained about breathing problems, burning eyes and nausea.

Firefighters designated special areas outside the airport where physicians examined those affected by the substance.

The cause of the incident was not known, airport spokeswoman Karen Stein said.

mb/jlw (AFP, dpa)