“YPF completely rejects the accusation made Monday by the government and is ready, as usual, to provide all explanations that the government could ask for, confident that its reputation and prestige will be intact at the end of this investigation,” it said in a statement late Wednesday.

The Argentine government said it suspects the oil companies of overcharging transportation companies by more than $800 million a year.

Shell was the first company to react, saying Monday that “it respects and will respect all rules established by law and is at the authorities disposal.”

Besides Repsol-YPF and Shell, Transport Minister Juan Schiavi singled out Esso, Petrobras, and Oil Combustibles as suspected of “abusing their dominant positions in the fuel market.”

“The amount is about 3.5 billion pesos ($808 million.) This figure is enormous and puts at risk two transport systems (freight and passenger),” said Schiavi.

For his part, Planning Minister Julio de Vido estimated the overcharges at “around 30 percent.”

In October 2011, the government forced oil and mining companies to repatriate all foreign exchange perceived from exports, rather than 30 percent as previously required, in an effort to stem capital flight.