Charles Sirleaf, the son of Liberia's former President Ellen Johnson Sirleaf, has been arrested in relation to the illegal printing of more than $104m (£78m) worth of local banknotes.
He was a deputy governor of the Central Bank at the time of the incident in March last year. Mr Sirleaf's former boss - ex-Central Bank head Milton Weeks - has also been detained.
Their lawyers are yet to comment.
The arrests come after a report into the missing millions was released.
The much-anticipated report, carried out by investigative auditing firm Kroll associates, was released by the US embassy on Thursday.
It was looking into the alleged disappearance of more than $100m (£75m) worth of newly printed Liberian banknotes last year.
It had been widely reported that shipping containers full of banknotes had vanished from Monrovia's port and airport. However the report did not find any proof that this happened.
Instead, it found that Liberia's Central Bank had acted unilaterally and unlawfully by printing and importing into the country three times the amount of banknotes it had been authorised to do.
What did the report find?
The country's Central Bank, which had received new banknotes in a total of 20 shipments, was not able to properly account for the money.
The bank was also unable to explain and present proper documentation on how the money was infused into the Liberian economy, the report found.
The banknotes were ordered before President George Weah came to power in 2018, but critics say his government had a hand in the poor handling of the consignment of banknotes - an allegation the administration has denied.
The report points to widespread inconsistencies, lack of proper documentations and explanation and a gross disrespect for money-ordering policy.
How much money was ordered?
According to Kroll, the House of Representatives passed a resolution for the order of 5bn Liberian dollars to remove and replace old banknotes on the market.
The Central Bank requested additional 10bn Liberian dollars but the request was denied by the Senate. The bank went ahead anyway and engaged a company to print the additional banknotes.
"CBL (Central Bank of Liberia) management subsequently explained to Kroll that due to the urgency for new banknotes, the CBL did not follow its own internal tendering policies for the procurement of Crane AB," the report says.
Kroll explains in the 67-page report that, despite repeated requests, the bank did not provide any explanation as to who had approved the injection of new banknotes into the Liberian economy without first removing the equivalent quantity from circulation.
What has the response been?
The US embassy says the report identifies "systemic and procedural weakness" at the Central Bank and suspects shortcomings in the country's fiscal and monetary management processes continue to this day.
The Liberian government also released its own report on Thursday, which similarly said that it had found no evidence of the existence of containers full of banknotes.
It said that an investigation needs to be carried out into a separate $25m that was withdrawn from Liberia's Federal Reserve account in New York in July last year by Mr Weah's economic management team.
In addition to the arrest of Charles Sirleaf and Milton Weeks, another man, an official at the Central Bank, Dorbor Hagba, has also been arrested.
They are yet to be formally charged.