The police said the cocaine, neatly packed into parcels, was found in one of six containers. The five remaining containers are still to be searched and police did not rule out that they, too, could contain drugs.
Interior Minister Euclides Acevedo said the final haul could amount to more than three tonnes.
Charcoal, a key Latin American export, has become a popular cover for trafficking cocaine across international borders.
While the containers’ final destination was marked as Israel, the shipment was due to make stops in the Argentine capital, Buenos Aires, and in the Belgian city of Antwerp, Mr Acevedo said.
A tip-off from Belgium reportedly alerted Paraguayan police to the drugs shipment in the first place.
Paraguayan counter-narcotics officials think the cocaine was brought to Paraguay by air from Bolivia, the world’s third biggest producer of the drug.
Paraguay has been a key transit country for drugs for years. Some of Brazil’s most notorious criminal gangs, such as First Capital Command (PCC), have expanded across the border into Paraguay.
Paraguay’s previous biggest cocaine haul was seized in February 2019 and weighed 2.2 tonnes. That time, the drugs were hidden in a vehicle in the northern Concepción region.