A joint operation by the Australian Federal Police (AFP), Australian Customs and Border Protection Service (ACBPS) and South Australian Police (SAPOL) resulted in the arrest of two people-including a member of the Gypsy Jokers motorcycle gang-in relation to the seizure of a semi-automatic firearm and approximately seven kilograms of cannabis, 38 cannabis plants and four litres of GBL.

A joint media release issued by the agencies said, 31-year-old Glanville man was arrested for importing the border controlled drug, gamma-Butyrolactone (GBL). GBL is commonly known for its use as a 'date rape' drug.

Further investigation by the authorities resulted in the 31-year-old male being charged with drug importation and firearm offences while another 22-year-old Glanville woman was charged with firearms offences.

The man was charged by the AFP with Import a Commercial Quantity of a Border Controlled drug. He was also charged by SAPOL with being an unlicensed person in possession of a firearm.

Meanwhile the woman was charged by SAPOL for possessing a firearm without a licence, and possessing an insecure firearm.

The media release said, further charges against both the accused is being considered.

The maximum penalty for importing border controlled drugs is life imprisonment and/or an $825,000 fine, the release added.

The joint operation began earlier this week when ACBPS officers intercepted a package containing eight bottles containing approximately four litres of a liquid labelled cleaning fluid.

Suspicious ACBPS officers sent the liquid for testing and found it was GBP. The release said, ACBPS officials then referred to bottles to AFP for further investigation.

On Thursday, the AFP and SAPOL Serious and Organised Crime Investigation Branch conducted a controlled delivery operation. The man took delivery of the package at a residence in Glanville and was later arrested while in a vehicle with the woman, the release said.

After further search of the vehicle, authorities discovered a firearm and a large amount of ammunition.

Later search by SAPOL at another associated residence in Burton discovered approximately 800ml of GBL, approximately seven kilograms of cannabis, 38 cannabis plants and hydroponic growing equipment, the release said.

AFP Manager Adelaide Office Mick Calatzis warned criminals who thought it was safe to import drugs through mail.

"If you try to bring in drugs through the mail system you face the combined efforts of a number of law enforcement agencies," Commander Calatzis said.

"This wasn't a small amount for personal use. GBL is a prohibited drug and four litres of this equates to thousands of doses and any one of those could have tragic outcomes for the user."

"The AFP will continue to work with our border and state counterparts to stem the supply of drugs such this," Commander Calatzis said.

ACBPS National Manager Cargo Operations Jagtej Singh commended the officers involved in the initial seizure and subsequent arrests.

"Our solid partnerships with the AFP and SAPOL are paramount in disrupting criminal activity of this nature," Singh said.