Esperanza Aguirre talks at an improvised press conference outside Madrid Popular Party headquarters. Samuel Sánchez

The Civil Guard raided the headquarters of the Popular Party (PP)’s Madrid branch on Thursday in search of incriminating evidence of illegal party financing.

Five homes were also searched, as well as the headquarters of Villar Mir, the parent company of construction giant OHL.

“There is no evidence and no proof of any kind of illegal financing”

The operation is part of an ongoing investigation into the Púnica case, a bid-rigging ring that was broken up in late October 2014 with the arrest of 35 people in several provinces.

The Púnica ring is believed to have unlawfully awarded as much as €250 million in public contracts whose beneficiaries had been predetermined by the ringleaders after accepting bribes from the corrupt bidders.

One of the main suspects in the case is Francisco Granados, once the right-hand man to Esperanza Aguirre when the latter was regional premier of Madrid.

Thursday’s court-ordered raid was triggered by notes kept by Granados in an agenda whose contents remain under seal. The case is being investigated by High Court judge Eloy Velasco.

Officers sent to the Madrid PP’s home on Génova street – inside the same building that houses national party headquarters – were looking for documents in the power of former party manager Beltrán Gutiérrez Moliner, whose own home was also searched. Gutiérrez Moliner is also involved in a parallel probe into secret credit cards issued by the Caja Madrid bank to top executives for discretionary spending.

Legal sources confirmed that Civil Guard officers also took away material from the Villar Mir Group, the parent company of construction giant OHL

The origin of Operation Púnica was the discovery of Swiss bank accounts held by Granados and David Margaliza, a businessman and childhood friend of Granados. Swiss authorities informed Spain about indications of “aggravated money-laundering operations” through accounts in which both men held a joint €5.8 million at one point.

Esperanza Aguirre, who is now the president of the PP’s Madrid branch, said the party was “cooperating all the way.”

“There is no evidence and no proof of any kind of illegal financing,” she added.

Legal sources confirmed that Civil Guard officers also took away material from the Villar Mir Group, the parent company of construction giant OHL. Handwritten notes found in Francisco Granados’ possession suggest that the company may have paid out large sums of money to the Madrid PP.

The name Villar Mir also crops up as a donor in parallel accounts kept by Luis Bárcenas, the former treasurer of the national PP. This larger investigation into unlawful donations and illegal party financing is one of the biggest corruption cases to affect the Spanish conservatives.