Weapons were found during a search of a residential building in Itzehoe (Schleswig-Holstein) on Sunday morning.
The explosive ordnance clearance service was therefore called in, according to the Itzehoe police.
A spokesman for the Kiel public prosecutor's office for the German Press Agency also confirmed the use of the explosive ordnance clearance service.
According to the public prosecutor's office, the search was related to a cross-border operation.
There have been searches in several federal states.
Five suspects are being investigated.
The investigations are at an early stage.
The chief public prosecutor did not comment on the allegation – nor on whether there were arrests.
According to information from the "Bild" a soldier of the Bundeswehr in Itzehoe "apparently have hoarded various weapons and explosives".
Among other things, bombs and mines are said to have been secured by the officials.
The Schleswig-Holsteinische Zeitungsverlag writes, citing unconfirmed information from several neighbors, that it is said to be a member of the Bundeswehr.
When asked by the dpa, the Federal Ministry of Defense in Berlin confirmed that there had been an "incident" in Itzehoe, but referred the details to the police authorities.
Initially, there was no confirmation from the Federal Ministry or from the public prosecutor that the person concerned was a soldier.