(Adds reactions from Caixabank and Repsol)
By Jesús Aguado
MADRID, July 29 (Reuters) - Spain's High Court has dropped a formal investigation into the chairman of oil company Repsol Antonio Brufau after it found no evidence of his alleged participation in a decade-old spying case, a court document showed on Thursday.
The investigating judge Manuel Garcia Castellon also dismissed an investigation against former Caixabank chairman Isidro Faine and the companies Repsol and Caixabank.
The High Court had put all of them under investigation as part of a probe into the case of alleged spying.
Both companies said they welcomed the decision by the court to close the probe and pledged in any case to fully cooperate with judicial authorities.
Castellon was investigating whether Repsol and Caixabank hired Grupo Cenyt, a security firm belonging to former police chief Jose Manuel Villarejo, to spy on the then chairman of construction company Sacyr, Luis del Rivero, in 2011 and 2012.
The alleged aim was to block a takeover bid for Repsol by Sacyr and Mexican state oil firm Pemex.
Repsol was then partly owned by Caixabank.
On Thursday, the court said "without evidence that the chairmen of the companies were directly involved in the events under investigation, it is not possible to put them under corporate supervision and oversight."
The court also said in its ruling that both companies had adequate measures in place to prevent the commission of the offences under investigation.
Castellon was investigating Brufau and Faine for any possible links to bribery, in connection with both companies' alleged dealings with Villarejo.
No formal charges had been brought as the probe was in its first phase.
The investigation is part of a wider inquiry, centered on Villarejo's activities, that has roiled Spain's corporate sector, causing some reputational damage, but with no clear impact on companies' businesses so far.
Spanish bank BBVA and Iberdrola Renovables Energia, a unit of power company Iberdrola in Spain, remain under investigation in relation to Villarejo's activities. (Reporting by Jesús Aguado Additional reporting by Emma Pinedo Editing by Inti Landauro and David Evans)
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