Equatorial Guinea has demanded that Brazil hand back more than $16m worth of cash and luxury watches confiscated from a delegation which accompanied the president's son, Teodorin Nguema Obiang to Brazil
Mr Obiang, who is vice-president of Equatorial Guinea, arrived in Brazil on Friday on board a private jet.
Brazil prohibits people from entering the country with more than $2,400 in cash.
Both Mr Obiang and his father deny misusing their country's oil revenue.
According to a report by CNN, Brazilian authorities seized more than $16 million in cash and luxury watches from the delegation which travelled with the vice president of Equatorial Guinea.
Teodoro Nguema Obiang Mangue, the son of the nation's longtime leader, was part of an 11-member delegation that travelled to the South American country.
About $1.5 million in cash and luxury watches valued at more than $15 million were seized by Brazil's federal police after searching their private plane, which arrived at the Viracaspos airport near Sao Paulo on Friday, a Brazilian newspaper media reported.
The 48-year-old vice president is the only member of the group with diplomatic immunity who was not included in the search operation.
Officials searched the plane and luggage of other members of the group, according to daily newspaper O Estado de Sao Paulo.
The money was to pay for a medical treatment Obiang was to undergo in the Sao Paulo and his hotel accommodation during his stay in the country, the newspaper reported, quoting an official of the Equatorial Guinea Embassy in Brazil, who was with the delegation at the time.
The luxury watches engraved with Obiang's initials, according to the report, are for the vice-president's personal use, the official added.
Brazil's Foreign Ministry said it was working with federal police and customs to determine steps that will be taken on the case, according to media reports.
Obiang has been accused of embezzling millions of dollars from oil-rich Equatorial Guinea to buy mansions, cars and fund a lavish lifestyle abroad.
In 2014, the vice president sold his Malibu mansion, a Ferrari and paid $20 million to a charity as part of a settlement deal following allegations that he had used public funds to amass the assets in the United States.
He was sentenced last year in France to a three-year suspended sentence on charges of embezzlement of public funds and money laundering.
Obiang's father - Teodoro Obiang Nguema, - has ruled the country for 39 years.