SAO PAULO (AP) — Brazilian police said Thursday that nearly 28 tons of marijuana have been seized hidden in corn in what authorities have called “the biggest drug bust” ever in the country.

The Brazilian federal police say several packages of the drug were underneath the corn being carried in a truck that was stopped by officers on a highway in the southwestern state of Mato Grosso do Sul on Wednesday.

Police say they had started monitoring the truck after suspicions were raised about its driver at a hotel in the city of Ponta Porã at the Brazilian border with Paraguay.

Police say the driver alleged the truck was already loaded when he picked it up and was taking it to the southern Brazilian state of Rio Grande do Sul.

The driver was arrested and will face drug trafficking charges.

Police didn't immediately release any other details.