Cuadernos de Espeleología II drew Matienzo to the attention of other clubs, and the first to visit the area was the Grupo de Exploraciones Subterráneas belonging to the Club Montañés Barcelonés. In summer 1967, a dozen cavers came to Matienzo, under the leadership of Juan Ullastre, with the particular aim of exploring the Vega sector in greater detail.
They returned to many of the caves SESS had published, such as Rascavieja or Patatal, and carried out a survey of Agua, where they also found a mammoth's tooth. They say they visited Cubio de la Reñada, without claiming any new passage, which seems strange as Fernández had left it wide open.
Their report features three new caves. First, Sima de los Rellanos in South Vega was descended to a depth of 120m. But their most important finds were in Cubija: Simas del Picón, and Torcón de Cubija. In the former they surveyed 450m, ending at the choke after the large boulder chamber. The length reached in Torcón was 334m. Local people remember them visiting Cubio de Cubija, but there is no mention of this in their report, which wasn't published until 1975.
The same club doesn't appear to have ever returned to Matienzo, although in 1976 they came to drop a number of shafts near the pass of Alisas. One of these is just within the limits of Matienzo, Sima del Roldán, where they reached -65m. They also descended Sima del Cueto, which had been done once by Speleo-Club de Dijón. This second survey gives it a depth of 126m.