Portuguese police have found an apartment in Obidos which is thought to have been used by members of ETA. Explosives and other materials were found on the premises.
The apartment had been rented out several months ago but when the tenants stopped paying the rent, the owner went to check on the property.
The police were informed and weapons, explosives, detonators and other materials were seized.
Two ETA suspects, Garicoitz Garcia Arrieta and Iratxe Ortiz de Barrón, were recently detained in Portugal after being stopped in Bermillo de Sayago while driving a van carrying explosive materials.
It is thought that ETA has been trying to reactivate its infrastructure in neighbouring Portugal.