Police have used forklifts to seize thousands of litres of chemicals used to make the drug GHB, in one of the largest such seizures in Victoria's history.

Officers said a family-run syndicate based in Craigieburn, in Melbourne's north, had been shut down after the discovery of 2,100 litres of a liquid chemical, known as 1,4-Butanediol or "bute", in drums at an industrial property in Craigieburn.

The chemicals were allegedly intended for use to make the drug GHB, and police said they were worth an estimated $10 million.

They also found another 750 litres of what is believed to be the same chemical, and 12 guns.

'It's not often you clear a crime scene with a forklift," said Detective Senior Sergeant Cocks. ( Supplied: Victoria Police )

"We've seized what we believe to be in excess of 2,100 litres of this product, which equates to be what we believe to be about a million doses on the street," said Victoria Police Superintendent Michael Grainger.

"We think this … is one of the largest seizures in Victoria's history.

"We believe it is likely to have a significant impact on public safety and community health."

Over 30 warrants were executed over a year in Melbourne and Shepparton.

"It's not often you clean a crime scene out with a forklift, but that's what we had to use," Detective Senior Sergeant Jeff Cocks said.

Six men and a woman are facing charges, including commercial drug trafficking and gun possession.

The syndicate was allegedly dealing drugs both in Melbourne and in country areas including Shepparton, Wangaratta and Cobram.

Victoria Police seized more than 2,000 litres of chemicals used to make the drug GHB. ( Supplied: Victoria Police )

GHB has been linked to dozens of overdoses at clubs and festivals.

"It's taken in liquid form, generally in very small quantities of about one millilitre, and has an initial euphoric effect on those that take it," Superintendent Grainger said.

"If taken to excess it can lead to death."

Superintendent Grainger said police were continuing to investigate the syndicate.

"They're certainly employing techniques designed to protect their business model," he said.

"They're sophisticated in their efforts to avoid detection by law enforcement agencies.

"We believe it's a familial-based organised crime network. Their sole purpose is to build profits from their illegal trade."

The drugs appear to have been sent into communities in northern Victoria via a series of runners, for others to sell in the local area.