Algeria's former police chief Abdelghani Hamel has been placed in provisional detention over alleged "diversion of funds and illicit enrichment", state television said Friday.
Hamel, who was fired in June last year, appeared before an investigating magistrate in central Algiers, it said.
Two of Hamel's sons were also detained overnight, while his wife was provisionally released in the same case, state television reported.
In total, the examining magistrate will question 19 people in the case, including ex-civil servants and real estate agents, according to the official APS news agency.
Former president Abdelaziz Bouteflika's decision to fire Hamel last year came as a surprise, since he had been viewed at the time by analysts and the Algerian press as a potential successor.
Hamel was fired due to a cocaine trafficking scandal, which tarnished numerous officials including magistrates.
The ailing Bouteflika was himself forced to step down on April 2, after weeks of street protests against his two-decade rule.
But protests have continued, demanding the fall of other regime insiders and the establishment of independent institutions ahead of credible elections.
Algeria's legal system has launched a series of probes into corruption and embezzlement, targeting state officials and powerful businessmen close to the ex-president.