French trader Jerome Kerviel, who allegedly cost banking giant Societe Generale €4.9 billion (Dh26.4bn) in losses, was taken into police custody in Paris on Saturday, a judicial source said.
Kerviel, 31, was being held for questioning after arriving in a car at the headquarters of the Paris police's financial brigade around 1pm GMT, said the source.
He had dropped out of sight since the bank announced its colossal losses on Thursday, which slashed the bank's 2007 profit to €600-800 million from €5.2 billion in 2006.
Police nabbed Kerviel from his vehicle in the underground car park of the financial brigade's offices in Paris, said a source close to the investigation.
The detention followed a police raid on Kerviel's apartment on Friday in the wealthy Paris suburb of Neuilly sur Seine during which documents were seized.
The French government has demanded a full accounting of the scandal over the bank losses, the biggest of their kind in financial history.
The Kerviel case dwarfs that of Nick Leeson, the "rogue trader" who lost $1.5bn (Dh5.5bn) at Barings, causing the failure of the venerable British bank in 1995. (AFP)
'Rogue trader' Jerome Kerviel in police custody: judicial source