As reported by RIA Novosti with reference to Twitter of the Federal Police at Frankfurt Airport, what is happening is associated with the discovery of abandoned baggage. 

It is specified that this baggage has already been inspected, it is recognized as safe.

At the same time, RND reports that two people were detained because of suspicious baggage, and the police are still looking for another.

Earlier it was reported that a police operation is underway at the airport of Frankfurt, Germany, which is why one of the airport terminals and the railway station was partially closed.