Under heavy elite police guard, the ex-leader was taken from his home in an exclusive residential area in the west of San Salvador and taken in a police car to the Anti- Narcotics Division yesterday, where he was confined to a cell, civil police deputy chief Howard Cotto told reporters.
"It is a normal cell, with nothing special and where the president will be alone," added Cotto, who had earlier escorted Flores himself to jail.
Flores, who was president of the small Central American country from 1999 to 2004, claims to be a victim of political persecution.
He is accused of embezzlement, illicit enrichment, and actions detrimental to public administration.
He was investigated by El Salvador's Congress as well as the attorney general's office after then president Mauricio Funes said US Treasury Department reports showed suspicious transfers by Taiwan to Flores between 2003 and 2004.