Heavily armed Canberra-based tactical police swarmed the back streets of sleepy Bungendore on Sunday morning, resulting in two arrests related to a $144 million cocaine shipment from South Africa.

The drugs arrived into Australia in a second-hand 20-tonne Caterpillar excavator, shipped out of South Africa and into Sydney's Port Botany container terminal.

Border Force officers were suspicious about the origins of the heavy equipment and X-rayed sections of it. "Anomalies" were found and investigated.

The cocaine was concealed within the hollow steel lifting boom. The void was filled with 384 one-kilogram packets of the drug, welded shut, and carefully restored to the factory colour.

The concealment was described by Border Force acting deputy commissioner of operations Sharon Huey as a "targeted detection" that was "incredibly sophisticated" and "very specialised".

"From the outside it didn't look like it had been tampered with at all."

She said it took two days for Border Force officers to cut into the arm, extract the drugs, substitute them and return the excavator to its original condition.

Operation Buxtahude was the name given to the controlled delivery to the Bungendore landscape supplies company, under surveillance by police. When police entered the Bungendore premises, simultaneous warrants were executed in Queanbeyan, where the arrests were made.

IN OTHER NEWS:

She described the size of the seizure as significant from a national perspective.

"To put this in perspective, in the 2017-18 financial year approximately 795 kilograms of cocaine were detected at the border; this 384 kilogram delivery represents almost half that amount," acting deputy Commissioner Huey said.

Chief Police Officer Johnston said "a range of information was provided" to Border Force partly from the public and through ACT police investigations.

It is suspected that the target market for the cocaine was Canberra, the South Coast and the Snowy Mountains region.

"I suspect this is not an insignificant hit to the syndicate; $144 million is a lot of income," Chief Police Officer Johnston said.

"In any of these criminal enterprises there are associations and connections and other syndicates working in cahoots . . . they inevitably will have their own enterprises so we have to stay on our toes to identify them."

As operations were ongoing, he would not comment further only that police "continue to stay interested in this particular syndicate".

"ACT Policing will continue to provide operational information and intelligence to the AFP national anti-gangs squad which will continue to work with our partners offshore."

The 384kg seizure is the biggest drugs interception made by ACT police, who coordinated the raid out of Winchester Police Centre in Belconnen in strict secrecy after having a regional crime syndicate under surveillance for some months.

Precautions were necessary because the syndicate had close links to a bikie gang, ACT Chief Police Officer Ray Johnston revealed.

After simultaneous search warrants in Queanbeyan and Bungendore, two men appeared in Queanbeyan Local Court on Monday as a result of the raid.

They are Timothy John Engstrom, 34, and Adam Phillip Hunter, 35, both of Queanbeyan. Neither man applied for bail, nor entered pleas. They will be held in custody until their next scheduled court appearance on September 9.

The two men are expected to face high-level drug trafficking charges, which potentially carry a maximum sentence of life imprisonment.

Australia is seen as a lucrative cocaine market because of the high price the drug fetches.