Rodrigo Rato, a former Spanish deputy prime minister and one-time head of the IMF, was taken into custody here Thursday after prosecutors charged him with fraud and asset laundering.

Personnel from the AEAT tax agency used an unmarked police car to transport Rato from his home to his office elsewhere in the capital.

A judge signed a warrant authorizing his detention to facilitate authorities' ongoing search of the Rato residence and additional investigative steps to be carried out at other locations.

Rato was not handcuffed when he left his central Madrid home.

AEAT launched the investigation after Rato sought to use the Spanish government's 2012 tax amnesty to regularize his assets, a process that exposed what prosecutors describe as a "complex network" of companies belonging to the former official's family.

Questions about the origin of Rato's wealth prompted his inclusion on a list of 705 people suspected of having used the tax amnesty to launder assets.

Rato served as economy minister and deputy premier in the 1996-2004 government of Prime Minister Jose Maria Aznar before being named as managing director of the International Monetary Fund, a post he held through 2007.