Billions of dollars were allegedly used for bribes in an unsuccessful bid to get ex-president Goodluck Jonathan re-elected.
Nigeria has recovered more than $500 million in cash and has seized over $9 billion in assets.
Hundreds of millions of dollars in Nigerian money have been secreted abroad.
The country's non-existent workers have cost Nigeria $5 million so far.
Waripamowei Dudafa is alleged of involvement in a $2.1 billion arms scandal in Nigeria.
The nonexistent workers were removed from the state payroll following an audit launched in December.
Some 20 people died in stampedes at a recruitment drive by Nigeria's immigration service in 2014.
After allegations of corruption and copies disappearing, Nigeria's budget fiasco goes on.
Allegations against Saraki include that he acquired wealth beyond his legitimate earnings.
Muhammadu Buhari is cracking down on corruption in the Nigerian government.
The government spokesman is accused of involvement in diverting $2 billion meant for fighting Boko Haram.
Members of Jonathan's government have been accused of stealing money earmarked for fighting Boko Haram.
President Buhari has ordered that 20 retired and serving military officials be investigated for corruption.
Information minister Lai Mohamed said ex-ministers and bankers were among those responsible.
Mohammed allegedly colluded with Sambo Dasuki to steal arms money earmarked for fighting Boko Haram.
Femi Fani-Kayode said "all hell will break loose" if the high-profile prisoners are harmed.
Sambo Dasuki allegedly awarded phantom contracts for arms to fight the Nigerian militant group.