In total, more than a tonne of illegal substances with a market value of at least €400 million was found at the plant.
The Chief of the Police Armands Ruks said that the investigation operation lasted more than a month and involved extensive resources, including Europol.
The police chief said that 8 persons had been detained in the operation, six of whom had been remanded in custody.
The detainees are aged between 24 and 35, five of them are Ukrainian citizens, two are Polish citizens and one is Armenian.
Police representatives did not comment on whether the group was linked to Latvian citizens.
"This is an international group. The laboratory has not been operating on the territory of Latvia for a long time. This is their way of operating, not staying in one place for a long time," Ruks said, without commenting specifically on how long the group had been operating in Latvia, but noting that "it is not years".
Criminal proceedings were carried out simultaneously in several Latvian cities, including seven searches.
In total, more than 38,000 litres of various chemical liquids, which according to expert opinion are precursors or base materials for the production of synthetic drugs, were seized, as well as laboratory equipment and various items related to the production of narcotics, 5 vehicles, and several mobile phones, SIM cards, routers, a laptop computer and other items relevant to the investigation were seized.
At the same time, police seized more than one tonne of the synthetic drug Clephedrone or 4-CMC. The Chief of the General Prosecutor's Office said that the total market value of the seized illegal substance is at least €400 million, and the price of the drug on the market is €20-25 per gram.
The drugs were not destined for the Latvian market, but possibly for other European countries, such as Scandinavia, as well as for the Russian and Belarusian markets.
Expert examinations are still ongoing to determine the precise weight and composition of the substance.
As Ruks pointed out, there were even larger stocks still in the chemical process, so it is assumed that the amount of finished products seized from the criminals will reach several tonnes once the forensic analysis is complete.
"These substances were packed in tanks and were in the last stage of the chemical process, i.e. crystallization. The forensic examination will determine whether they belong to the finished product or not. If it is a finished product, then we can calculate that about a couple of tonnes of finished narcotic substances will be added to the already finished crystalline substance," the police chief said.
This criminal offense is being investigated in criminal proceedings initiated under Article 253.1(3) of the Criminal Law - for the illicit manufacture, acquisition, possession or transport of narcotic drugs and psychotropic substances for the purpose of realization, if committed by an organized group.