Parts of Frankfurt Airport have been evacuated and boarding has been halted in some areas after someone got past security into the boarding areas, federal police said on Tuesday.

“At least one unauthorized person has entered the security zone,” a spokeswoman for the federal police told Reuters.

German airline Lufthansa, whose main hub is in Frankfurt, said on Twitter that boarding had been stopped at the A and Z levels of the airport’s Terminal 1.

It said it could not yet say how many flights might be delayed or cancelled as a result of the evacuation.

On July 28, some 300 flights were cancelled at Munich airport, Germany’s second biggest after Frankfurt, affecting more than 30,000 passengers, after a similar incident in which a person passed through the security area without being checked.