Nineteen people were arrested as part of the operation in the raid, which found underground laboratories illegally producing dietary supplements and counterfeit drugs.

Polish Police reported an organised crime group had been operating for three years, smuggling large amounts of material from Asian countries used to illegally produce drugs.

Prohibited anabolic and androgenic steroids, several hundred packages of new psychoactive substances, around one tonne of raw materials used in illegal production and cash were seized.

Property totalling €3.5 million (£3 million/$3.8 million) was also seized from the suspects.

The operation received support from POLADA and the World Anti-Doping Agency (WADA).

It is not believed to have any connection to the ongoing Kraków-Małopolska 2023 European Games here, where POLADA is managing the anti-doping programme with the International Testing Agency and a WADA independent observer team is in attendance.

The operation follows a €1.43 million (£1.23 million/$1.56 million) grant awarded to WADA by the European Commission last year to increase intelligence and investigation capacity in Europe, a project which covers 48 countries.

WADA director of intelligence and investigations Gunter Younger explained the concept of bringing together National Anti-Doping Organisations (NADOs) and law enforcement agencies, and claimed the project had been more successful than anticipated.

"When we started this concept of bringing law enforcement and NADOs together, we expected perhaps two operations together, but we have exceeded that and more are ongoing," Younger told insidethegames.

WADA President Witold Bańka argued the raid was a successful example of collaboration with law-enforcing bodies.

"The World Anti-Doping Agency is delighted to have contributed to this sophisticated, multi-party operation through our intelligence and investigations department," the Polish official said.

"Since its formation in 2016, this team has played a pivotal role in the protection of clean sport, leading several successful investigations, across a range of countries and sports.

"This latest operation is the result of excellent collaboration between several organisations, including WADA, the Polish Anti-Doping Agency and law enforcement in a number of European nations.

"Increasingly, these kinds of collaborations with various law enforcement agencies, including Europol, Interpol and customs authorities, are bearing fruit and delivering results for the athletes of the world.

"I congratulate the police and all those involved, and I pledge the ongoing support of WADA to help restrict the global production, sale and supply of performance-enhancing drugs."