Parts of Frankfurt Airport in Germany were evacuated for several hours after a family were allowed to walk through security despite testing positive for explosives.

Federal police stopped flights from boarding and kept passengers out of area A of the airport’s Terminal 1 for about two hours, over concerns at least one person had entered without being properly screened.

“The cause of the evacuation of the terminal was an error by a security officer. Despite a positive test for explosives, a French family of four were allowed to leave the security zone,” police said on Twitter.

Passengers described scenes of “confusion” as they were evacuated from the terminal at Germany’s busiest airport.

Adam Miller said on Twitter: “Still crazy, people are exiting. Just a bunch of confusion, fortunately no panicking.”

The family were located, questioned and allowed to continue on their journey, the police added.

The terminal reopened around two hours after the partial evacuation and passengers, as well as airport and airline employees, were allowed to return.

The police gave no details on what triggered the positive explosives test.

Some 1,500 flights had been scheduled to take off and land at Frankfurt on Tuesday, according to airport operator Fraport.

It was not immediately clear how many flights were cancelled or delayed as a result of the evacuation.

Lufthansa said it was working on a new flight plan and would provide more information later on Tuesday.