(Repeats July 14 story with no change)

LONDON, July 14 (Reuters) - The owners of Nabiax, a Madrid-based operator of computer data centres, are exploring a sale of the group that could value it at close to 1 billion euros , people familiar with the matter told Reuters.

Infrastructure fund Asterion Industrial Partners, which owns 80% of Nabiax, has engaged bankers at BBVA and Citigroup to gauge interest in its holding, said the people, who spoke on condition of anonymity.

Junior partner Telefonica may also sell its 20% stake as part of any deal, they said.

A sale process is expected to kick off after the summer lull, one of the people added. However, the plans may still be changed or dropped, the people cautioned.

Data centres are facilities that host IT systems and applications. Investors have been drawn to these assets, as the use of data grows and businesses outsource their IT infrastructure.

In April, Brookfield Infrastructure acquired French data centre group Data4 in a deal said to have valued the company at close to 3.5 billion euros, including debt.

Besides ongoing consolidation in the sector, the possible sale of Nabiax also comes amid efforts by Madrid to attract more than 6 billion euros in investments to establish itself as a data centre hub.

Asterion formed Nabiax in 2019 through the acquisition of 11 data centres from Telefonica across Spain and Latin America.

In March, the group sold its Latin American operations to British infrastructure fund Actis, with a view to focusing on its home market.

It is targeting 120 megawatts of installed capacity in Spain in the coming years, according to a press release at the time.

A sale of Nabiax could help Telefonica pay down debt, a focus for the Spanish telecoms giant.

Telefonica has accelerated its deleveraging efforts by selling non-core assets such as its tower division and stakes in some Latin American businesses. ($1 = 0.8905 euros) (Reporting by Pablo Mayo Cerqueiro, Amy-Jo Crowley and Andres Gonzalez in London; Additional reporting by Jesus Aguado; Editing by John O'Donnell and Louise Heavens)