MADRID (AP) — Tax agents spent a second day Friday searching the office of former International Monetary Fund chief Rodrigo Rato after he was briefly detained as part of a probe into alleged fraud and money laundering.

Rato, once one of Spain's most prominent politicians, went on his own to his office to be present during the second search.

On Thursday, Rato was detained by agents while they searched his apartment. He was then taken in an unmarked police car to his office for the first search before being allowed to return home.

A spokesman for Madrid's regional justice tribunal said Friday that prosecutors are investigating Rato for possible fraud, money laundering and asset concealment but declined to provide more details. The probe is being conducted under a secrecy order.

While Rato has not been formally charged, he is expected to be called before a judge soon, said the spokesman, who spoke on condition of anonymity because of tribunal rules preventing him from being identified.

Rato was Spain's economy minister and a deputy prime minister under conservative ex-Prime Minister Jose Maria Aznar between 1996 and 2004. He headed the IMF from 2004 to 2007.

He is also under investigation for his former role as chief executive of Spanish bank Bankia, which was bailed out in 2012. He has been suspended from the ruling Popular Party.

The searches followed Spanish media reports this week that Rato allegedly applied for a 2012 tax amnesty that authorities believe may have been used by some for money-laundering purposes. El Pais said Rato declined to confirm or deny the reports.

Finance Minister Cristobal Montoro said the latest investigation concerning Rato was not linked to the amnesty.

A series of scandals have outraged Spaniards and battered the Popular Party as it prepares for municipal and regional elections next month and general elections by the end of the year.

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Alan Clendenning in Madrid contributed to this report.