The headquarters of the Spanish bank BBVA are seen in Madrid, Spain, June 12, 2018. REUTERS/Juan Medina

MADRID (Reuters) - Spanish bank BBVA BBVA.MC said on Thursday it was investigating reports that it had hired a former police chief in 2004 to privately investigate top executives of a would-be buyer as well as a senior government official.

News websites El Confidencial and Moncloa.com reported on Wednesday that Spain's second-biggest bank had hired Jose Manuel Villarejo's firm, Grupo Cenyt, to investigate officials of construction company Sacyr SCYR.MC as part of efforts to stop a takeover bid by the company.

The media reports did not say how many Sacyr officials were investigated but said BBVA also hired Grupo Cenyt to investigate Miguel Sebastian, then chief economic adviser to then prime minister Jose Luis Rodriguez Zapatero.

“With regards to media reports related to Grupo Cenyt, which if found to be true would be extremely serious, BBVA informs that in June 2018 it opened an investigation into the hiring and services rendered by this company,” the bank said.

The bank said it had also hired an external law firm to conduct an independent review into the issue.

“Should any irregularities be detected during these reviews, BBVA will adopt the pertinent internal measures and take the appropriate legal actions and, as always, will fully cooperate with law authorities.”

It did not comment on the specific allegations made by El Confidencial and Moncloa.com.

Sacyr launched a takeover bid for BBVA in 2004 but it was not successful.

Villarejo was arrested in November 2017 as part of a separate investigation into alleged corruption, which has not yet been resolved.