Three people were arrested after drugs with an estimated value of R3.4m were found on a bus in Upington, Northern Cape, the Hawks said.

Provincial Hawks spokesperson Nomthandazo Mnisi said the trio were arrested on Monday during a disruptive operation.

Mnisi said the Intercape bus was intercepted after the team received a tip-off. 

The drugs included Mandrax tablets, dagga and tik.

Mnisi said the two bus drivers and a passenger are expected to appear in the Upington Magistrate's Court on Wednesday.

Intercape said the bus was travelling between Johannesburg and Cape Town via Upington.

"Intercape received an anonymous tip-off phone call and immediately contacted the Upington narcotics bureau.

"Due to legal limitations we cannot confirm any matters under police investigation at this stage. We can, however, confirm that Intercape is also conducting its own internal investigation into the matter," the bus service said.