Two Victorian men will face court after 139 kilograms of cocaine were found hidden inside luxury buses in an international shipment that arrived in Adelaide, with border force officials saying cocaine shipments are being seized in the country at "unprecedented levels". 

A joint investigation between Australian Federal Police (AFP) and Australian Border Force (ABF) stopped the shipment with "an estimated street value of $45 million" from entering the Australian community.

'Operation Silkwood' received intelligence that an alleged importation of cocaine was onboard a consignment of 13 luxury buses onboard an international cargo ship.

While police cannot confirm the origins of the drugs, the vessel, The Greatest Ace, arrived in Adelaide from Singapore via Perth.

On January 28, ABF maritime officers and WA detectives boarded the ship at Fremantle Port.

"[They] located a suspicious package wrapped in plastic in the roof end in one of the buses," ABF Superintendent Andrew Dawson said.

"Narcotics detector dogs gave a positive reaction to the package and the presumptive testing returned positive for cocaine.

"Officers contacted Australian Federal Police and proceeded to search the remaining buses, where a total of 139 packages were located, secreted in various void spaces inside the buses."

AFP Detective Superintendent Melinda Adam said the illicit drugs were substituted by AFP forensic officers with an "inert substance" in Perth.

"The buses were offloaded upon their arrival into Adelaide and stored in a car park in the Mansfield Park area," she said.

Two men allegedly forced entry into the buses and retrieved the drugs on February 3. 

Yousif Al-Asadi, 22, and Rayn Sadik, 19, who were arrested at a hotel in Port Adelaide, faced the Port Adelaide Magistrates Court on Monday afternoon charged with possessing a commercial quantity of a border controlled drug.

The defence lawyer for both men made no application for bail.

The pair from Victoria have been remanded in custody to face court again later this month.

Police urged anyone with information about unusual activity in or around the Port Adelaide or Mansfield Park areas on Friday February 2, and the following day, to contact Crime Stoppers.

"Any information, no matter how small, may lead to more arrests or continue to support our investigation," Superintendent Adam said.

"I will confirm that we are engaged with our law enforcement partners offshore to try and establish what part these men played in an offshore criminal syndicate.

"Let me make it clear, the AFP is a formidable and ever-present organisation and constantly monitoring serious and organised crime and the tentacles ... spread the globe."

Superintendent Adam said the bust was the second-largest seizure of cocaine in South Australia.

Superintendent Dawson said border officials had seen a "marked increase" in cocaine detections.

"Cocaine shipments are being seized at the nation's borders at unprecedented levels as Australia confronts a global surge in trafficking," he said.