Tunisian state TV showed images of what it said was gold and jewellery found in possession of the arrested members of Ben Ali’s family.
"Investigations will be carried out in order for them to face justice," a statement read out on state television said, citing an "official source".
Tunisian prosecutors have opened a vast inquiry into domestic and foreign assets held by Ben Ali, who fled to Saudi Arabia last week.
"Together we can write a new page in the history of our country," Foued Mebazaa said in an address to the nation on Wednesday. Tunisia’s government came under fire almost immediately after its formation for giving key cabinet posts to former allies of the deposed president.
All eight ministers concerned on Thursday resigned from Ben Ali's RCD, following the example of Prime Minister Mohammed Ghannouchi, who quit the party on Tuesday.
Three ministers belonging to the country’s powerful UGTT trade union pulled out within 24 hours of the formation of the cabinet to denounce its leadership.
The cabinet was set to meet for the first time on Thursday with ministers hoping to convince the unionists to return to the government.