Cocaine, heroin, amphetamine and cannabis were found by officers in a building in Larkfield Industrial Estate, Greenock, around 12.30pm yesterday.
Strathclyde Police said the drugs had a street value of more than £620,000, and officers are trying to trace those involved in their production.
Chief Superintendent Alan Speirs said: "This was an intelligence-led operation as part of our recently launched initiative Operation Myriad, which aims to target all aspects of criminality including drugs and drug dealing in our communities."
The five-month operation was launched in October to tackle violence, disorder, anti-social behaviour, organised crime, road traffic and drug offences.
Officers have been working with HM Revenue and Customs, ScottishPower, British Transport Police and communities to cut offences.
It follows Operation Neptune which targeted crime in the north and east of Glasgow between April and August last year. Police said it led to a significant drop in crime compared to the same area the previous year.
A number of drug seizures and arrests across Strathclyde have already been made under Operation Myriad.