By Daniel Schweimler
BBC News, Buenos Aires
Argentine authorities have issued an arrest warrant for a Venezuelan man over a cash-stuffed suitcase.
Mr Chavez signed energy deals with Argentina's Nestor Kirchner
They want to question Guido Antonini Wilson, who tried to bring $800,000 (£400,000) into Argentina as Venezuelan President Hugo Chavez was visiting.
Mr Antonini Wilson arrived with senior Venezuelan and Argentine oil executives and an Argentine government official.
Venezuela has denied involvement in the case, which has become known as "the scandal of the man with the briefcase".
Mr Antonini Wilson is a Miami-based Venezuelan businessman known as El Gordo, or The Fat Man.
He arrived in the Argentine capital, Buenos Aires, on a private jet 10 days ago, with executives from Energia Argentina and Venezuela's state oil corporation PDVSA just before Mr Chavez arrived in the city to sign an energy deal.
Mr Antonini Wilson was carrying $800,000, which he failed to declare.
He was fined $400,000 and promptly disappeared.
The Argentine government wants explanations but Venezuela's government says it has nothing to do with the case.
The Argentine official on the plane, which was chartered by the government in Buenos Aires, has resigned.
Media in both countries are investigating the movements of Mr Antonini Wilson, who travels extensively in Latin America - often with senior Venezuelan officials.
Argentina has been plagued with government scandals in recent weeks and is keen to avoid another, just weeks before elections.
Meanwhile, the scandal of "the man with the briefcase" has soured what looked like a strong friendship between Venezuela and Argentina.