A fraud probe into former IMF head Rodrigo Rato, which has embarrassed Spain's conservative government, made headlines again Tuesday following the arrest of a suspect in the case as he was about to board a plane for Mexico.

Rato, a former finance minister with the ruling Popular Party, has become a symbol of corruption among Spain's elites which has fuelled the rise of new parties ahead of a general election later this year.

Police on Sunday detained the head of a company Rato owns, Albisa, which Spanish authorities suspect acted as a front company to collect illegal commissions, judicial sources said.

The man was about to board a flight at Madrid airport for Mexico when a judge ordered he be held without bail and his passport withdrawn because of the risk that he could destroy evidence and flee.

Rato has been declared a formal suspect in two fraud investigations related to his time as chief executive at Bankia, a Spanish lender which was bailed out by the government in 2012.

The near-collapse of Bankia almost brought down Spain's whole financial sector, which later that year received 41 billion euros ($44 billion) in European aid.

Rato made headlines again in April when he was briefly arrested as part of another investigation into allegations of tax fraud and money laundering. He has denies any wrongdoing.

The case further embarrassed the government when it emerged that Interior Minister Jorge Fernandez Diaz held talks with Rato, a former leading light of the ruling Popular Party, at his office on July 29.

The minister on Friday denied interfering in the legal case against Rato, telling a parliamentary committee that the former IMF chief had sought the meeting with him because he had received threats.

Spain's National Office of Fraud Investigation suspects Rato of having collected commissions from companies that received Bankia contracts when he was the head of the lender, and of having bought a hotel in Berlin with the money, according to sources close to the investigation.

Rato, 66, was Spain's finance minister in the late 1990s and managing director of the IMF from 2004 to 2007.