Police have discovered chemicals worth $500 million in regional Victoria which they believe were to be turned into tonnes of methylamphetamine.

A 200-acre rural property in the Wimmera area was searched by the Horsham Clandestine Lab Team and Criminal Investigation Unit on Tuesday.

Police said they found more than 50 drums of methylamphetamine precursor chemicals weighing more than 10 tonnes and seized two unsecured firearms, ammunition and a small quantity of methylamphetamine.

A 59-year-old man was arrested at this address and later released.

The discovery is part of a 20-month investigation into an alleged drug trafficking operation in Victoria, with police shutting down three clandestine laboratories in Coburg North, Pascoe Vale and Monegeetta during that time.

A 44-year-old Newport man was also charged earlier this year in connection with the operation, after a man and woman allegedly transported 6 kilograms of MDMA hidden in a sleeping bag onto the Spirit of Tasmania ferry at Geelong Harbor in August. 21.

He was charged with trafficking a large commercial quantity of MDMA and was remanded to appear in Melbourne Magistrates Court later this month.

As part of the investigation, which began in February last year, officers also recovered more than $1 million in stolen vehicles and motorcycles that were being used in a revival operation, seized eight firearms and charged eight people.

They also seized commercial quantities of methylamphetamine, amphetamines and cannabis.

Investigations are ongoing.