The Guardia Civil has so far located 200 kilos of explosives and bomb making materials following the arrest in Bilbao of four suspected ETA members.
The four detainees are Iñigo Zapirain, Beatriz Etxebarria, Lorena López and Daniel Pastor and police are now trying to establish whether they were connected to a number of bombings and other attacks in Vizcaya in recent years.
It is currently believed that the detainees are connected to attacks in Burgos and Cantabria, the most serious being the destruction of the barracks in Burgos where a car bomb injured 65 people.
In addition, it is suspected that the detainees could have been involved in at least three other bombings in the Bilbao area as well as being implicated to some extent in the murder of Eduardo Puelles García.
Puelles, a 49 year old father of two, died when a bomb was attached to his car on June 19th 2009 in the town of Arrigorriaga (Vizcaya). Puelles was head of the Bilbao Information Brigade and was involved in combating terrorism.