Algerian authorities are embarking on a "Clean Hands" campaign aimed at rooting out corruption that has been linked to top tycoons and current and former government officials.
Corruption is a major complaint of the masses of protesters who helped drive longtime leader Abdelaziz Bouteflika from office earlier this month. New protests are scheduled for Friday.
Several influential Algerians have been questioned or arrested in recent days. Among them is Issad Rebrab, head of Algeria's biggest private conglomerate Cevital, who is suspected of possible customs-related violations and other financial wrongdoing, according to prosecutors.
Rebrab, 75, is estimated by Forbes to be Algeria's richest man and employs 18,000 workers in his agribusiness empire.
He tweeted that he went in voluntarily for police questioning. He was questioned for six hours before being taken to the El Harrach prison.
Others targeted include a legislator accused of accepting bribes from a Chinese company.
Also detained for questioning this week were three wealthy brothers believed close to Bouteflika's brother Said, and seven Industry Ministry officials suspected of "non respect of contractual commitments with state enterprises" and influence trading.
The Kouninef brothers' lawyers said they are respecting the legal procedures but need time to consult the case files before commenting. The brothers made their fortune in the oil, food and advertising businesses.
The highest court in Algeria announced in a statement Wednesday that it is considering a case against ex-energy minister Chakib Khelil for acts related to "violations of foreign exchange laws and transfers of capital to foreigners." Khelil is a close friend of Bouteflika and a high school classmate.
Other former ministers are also targeted.