According to Bavarian radio BR, the source of this contamination is firefighting foam that has been used for decades in routine fire training at military installations across the country.
The foam is known to contain dangerous per- and polyfluorinated chemicals (PFCs), which seep into the groundwater and may get into crops grown at nearby farms.
The radio said it had assessment reports that showed the problem to be greater than previously thought.
Contamination has been confirmed at 18 military sites, with 108 others under suspicion.
One of such bases is Ingolstadt-Manching in Upper Bavaria.
The PFC concentration there exceeds the allowed amount by a factor of 400. Residents in the commune of Manching are not allowed to use well water, and any soil dug out to make cellars is classified as hazardous waste.