Jannet Almeida, who is imprisoned at the headquarters of military intelligence in Caracas, is the second Venezuelan to be arrested in association with the case following the April detention of businessman Josmel Velasquez on money laundering charges.
"The woman was in charge of seeking customers to invest illicit funds in outsourcing-type business arrangements," the prosecutor's office said in a statement late on Friday.
Almeida will be charged with illegally obtaining funds in violation of banking regulations, the statement said.
Reuters was not immediately able to obtain comment from Almeida on the case.
A raid on her Caracas home in late May turned up Mossack Fonseca documents and incorporation documents for offshore companies, the prosecutors' statement said.
News reports based on millions of leaked Mossack Fonseca spurred global criticism that the firm was helping the rich and powerful to use offshore companies to evade taxes and launder money.
Mossack Fonseca, which specializes in establishing companies in tax havens, says it has not violated any laws or destroyed documents.