A 48-year-old man was arrested and charged after a mysterious bag, allegedly containing cannabis, was found strapped under the B-trailer of a Victorian truck.

Roads and Maritime Service (RMS) inspectors called police shortly after they stopped the north-bound vehicle, near Coolac on Wednesday afternoon. 

Traffic and Highway Patrol Command officers later located the bag and allegedly seized almost 10kg of what is believed to be cannabis.

The driver, a Queensland man, was taken to Gundagai Police Station and charged with supply prohibited drug – indictable quantity – and possess prohibited drug.

He was refused bail to appear at Wagga Local Court. 

In addition to the charges, the driver is alleged to have exceeded his work hours.

Assistant Commissioner Michael Corboy of the state's Traffic and Highway Patrol Command said that those using our roads to commit crime will be identified and prosecuted.

"Whether it’s our traffic and highway patrol officers, or RMS inspectors intercepting vehicles, those that are transporting contraband will be put before the courts,” Assistant Commissioner Corboy said.

"Whilst our focus will always be road safety, interstate drivers that think they can use our highways for their own benefit should think again.”

RMS compliance director Roger Weeks said it was another example of NSW Police and compliance inspectors working together to remove unsafe and illegal practices from the NSW road network.

“This routine inspection has enabled us to identify an issue of extreme concern to the motoring public,” Mr Weeks said.