According to their own statements, investigators from Baden-Württemberg prevented a bomb attack in Switzerland.
Special forces temporarily arrested two men when they wanted to buy the alleged explosives in Stuttgart, as the public prosecutor and the Baden-Württemberg State Criminal Police Office announced on Thursday.
The Swiss at the age of 24 and 26 would be strongly suspected, it said in Stuttgart.
The evidence so far suggested that the men wanted to use the explosives "presumably in a planned crime in a large Swiss city".
So far, however, there is no evidence of a politically motivated background to the planned crime.
No further details about the plan were initially given.
Both men have been under investigation since the beginning of the month.
The authorities got on their trail through a tip and through investigations in the so-called Darknet, a hidden and anonymous part of the Internet.
According to their own statements, they came across a user who wanted to buy explosives, among other things.
Arrest warrants were issued for the men last Tuesday.