Ten people were arrested when police stormed two adjacent double-storey houses in the central state of Selangor, early on Thursday morning, Malaysia's The Star newspaper said.
Firearms and several rounds of ammunitions were found together with tonnes of chemicals believed to be ketamin, syabu and heroin, ingredients for the manufacture of Ecstasy pills.
The raid followed a tip-off on Tuesday of a parcel containing what is believed to be syabu at the Kuala Lumpur International Airport, destined for East Malaysia.
Police traced the source to a house, arrested two men, one of whom was believed to be the main player in the drug operation.
The main suspect then led the police to two adjacent houses in another residential estate where the laboratory was housed.
The size of the haul was so large that even after 10 hours of inventory audit, the police were still unable to ascertain its value.