The discovery was made around 9pm, as agents were conducting a routine inspection.
The drugs were found under the floor of the bus, in a compartment located in the isle of the vehicle, according to the Ministry of Public Security.
The dog, which was supervised by an officer of the Drug Control Police (PCD, in Spanish), detected the presence of narcotics while inspecting the luggage compartment, which had been emptied. After the dog gave the alert, agents carried out a more thorough inspection, leading them to find the hidden compartment in the isle.
Three men identified by the last names Esquivel, Chacon and Aguirre, who were in operating the tourist bus, were arrested on suspicion of narcotics trafficking.
The bus belongs to a company that conducts tourism excursions. On December 25th a group of 27 passengers, most of them from San Jose, boarded the bus to travel to Panama on a shopping trip.
The tourists, who returned to Paso Canoas on the Panama border Friday night, were startled upon seeing the large number of police officers. Some female passengers began to cry upon learning that the bus was transporting narcotics.
When authorities questioned the passengers, they stated that the drivers would drop them off in all of the places that they were scheduled to visit, and would pick them up 4 hours later to return them to their hotel.
Police stated that none of the passengers were involved in the case.