Austrian authorities on the weekend said that recent raids had led to the seizure of 70 automatic and semi-automatic firearms, explosives and more than 100,000 rounds of ammunition.
German Interior Minister Horst Seehofer said Berlin had been cooperating with Vienna since October on the case.
He called the discovery of “such a great quantity” of weapons, munitions and explosives “alarming” and pledged a full investigation into the case.
“This is particularly true for the right-extremist background of the suspect in Austria,” he said in a written statement.
Last weekend, Austrian Interior Minister Karl Nehammer said the investigation had revealed “a network that shows links between the area of right-wing extremism and organized crime.”
He said that some of those belonged to the “neo-Nazi scene that has sadly also been known in Austria for a while.”
Austria's APA news agency reported that the weapons included submachine guns, assault rifles and handguns.
“The suspicion that the weapons and ammunition were intended for Germany requires a complete and comprehensive investigation,” Germany's Interior Ministry said.
The Interior Ministry said no further details of the find or the arrests could be released so as not to jeopardize the ongoing investigation.