The cache was found in the rural Irun area in the Basque country, the statement said, adding that it was not used in any recent time and was probably meant for some group of ETA terrorists.
The location was cordoned off, the statement added, stressing that the stash could be just one of the many in the region.
ETA, or Euzkadi Ta Askatasuna (Basque Country and Freedom) was an armed nationalist group founded in 1959. The goal of the organization was to gain independence for the Greater Basque Country. Since its foundation, the group has been held responsible for killing 860 people, and is considered as terrorist in Spain and several other countries, as well as in the European Union. In 2011, the group announced a "definitive cessation of its armed activity," with the Spanish government demanding complete disbandment of the group.