The arrest followed Salgado's resignation as BES executive chairman last month amid a spate of revelations, starting with news of accounting irregularities at the Luxembourg-based holding company Espirito Santo International.
His departure after three decades in charge marked the end of the family's control over the financial group set up almost 150 years ago by Salgado's great-grandfather, the abandoned orphan Jose Maria do Espirito Santo e Silva.
"The implosion of the Espirito Santo Group is the end of an era," commentator Luis Marques wrote Saturday in the weekly Expresso newspaper. "The detention of Ricardo Salgado is the moment that underscores that, it's a date that will go down in history."
Repercussions were swift as it became clear that the complex web of companies surrounding the family had been used to hide billions of dollars in debts that could no longer be paid.
Three family companies have been forced to seek bankruptcy protection. The authorities in Luxembourg, Panama and Portugal are investigating suspicions of further irregularities.
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A planned $17-billion merger between Portugal Telecom and Brazil's biggest phone operator Oi had to be revised to the Portuguese company's disadvantage after an Espirito Santo sub-holding called Rioforte defaulted on a loan to PT worth more than $1 billion.
Doubts about BES's local unit in Angola led the government there to issue a state guarantee of $5.7 billion to cover 70 percent of loans issued by Banco Espirito Santo Angola, a major player in the oil-rich African state.
In Europe, initial revelations of BES's troubles led to market panic. The bank's own shares have tumbled more than 70 percent since April. Fears a BES collapse could have a systemic impact on the euro zone hit markets in Spain, Italy and beyond.
However, the swift appointment of a new management team that's not linked to the Espirito Santo family has calmed concerns. Reassurance has also come from the news that Goldman Sachs and New York-based hedge fund D.E. Shaw bought into the bank last week. On Friday, the ratings agency Moody's upgraded Portugal, saying the BES scandal would not add to the country's credit risk.
"The new management has calmed markets," says financial journalist Maria Joao Gago, co-author of a book on the BES story that's topping best-seller lists. "BES has a long way to go to get back in shape, but there's a feeling that the damage will be limited to BES."
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In the old days, the Espirito Santos might have used their extensive political connections to wriggle out of their hole.