An estimated #1 million in counterfeit bank notes was seized by police during raids on properties across the West Midlands.
The operation, described as one of the largest seizure of its kind in the Midlands, also recovered sophisticated equipment and chemicals used to make money.
In addition, officers found a "substantial" quantity of genuine UK and foreign currency, suspected false credit cards, false identity documentation and a sports car number plate.
The haul was recovered by officers from Harborne police station and the West Midlands Police Economic Crime Unit during searches at properties in Smethwick in Sandwell, Nechells and Handsworth in Birmingham on Friday night and Saturday morning.
The police operation followed the arrests of two men in Icknield Street, Hockley, Birmingham, on Friday evening. At least seven people were detained as part of the inquiry.
Last night Detective Inspector Simon Wallis, from the Economic Crime Unit, said officers found "production factories" at the properties.
"This is a significant intervention in a serious criminal conspiracy involving highly professional and organised criminals," he said. "It was a substantial operation and a mixture of equipment was discovered. This is the largest seizure of the sort that we are aware off in the Midlands region and we are liaising with the Serious Organised Crime Agency.
"It was a very professional outfit, which operated in a very co-ordinated manner. The equipment was recovered at a number of addresses, where there were complete production factories."
Det Insp Wallis said counterfeit notes generally entered the system through the black market and when people dealt with the sale of illegal goods, they were not in a position to contact the police in the event of being handed fake bank notes as payment.
He added that the unit would be liaising with other forces across the country as part of their investigations. "Counterfeit currency is a significant threat to the UK economy and affects all of us. "There are some risks for people if they are given these notes and believe them to be genuine and when they are discovered to be counterfeit, we just lose them - they go out of circulation and we lose that money. We have potentially prevented the circulation of an estimated #1 million in counterfeit notes.
"A million pounds in counterfeit UK sterling - #20 and #50 denominations -- was discovered and we have also found a significant number of euros, which may also be counterfeit.
"Also, false identification documents including passports, driving licences and fraudulent credit cards were discovered. It has highlighted a number of individuals who were quite involved in these activities."
Det Insp Wallis said they could not comment on whether there were similar searches in other parts of the region or give any details about the people arrested.
* Three people were still being questioned by police last night while a woman was released on Saturday without charge.
Three others have been charged in connection with the raids and are due to appear at Birmingham Magistrates' Court today.