Three people were arrested when police broke up an elaborate Montreal-based counterfeit operation specializing in the production of fake American currency, the RCMP said Tuesday.

The raid on a printing shop in the Montreal suburb of Dorval netted close to $3 million in fake bills, the Mounties said, making it the biggest counterfeiting bust in seven years.

Impressed with the quality of the forgeries seized, Sgt. Andre Bacon of the RCMP Counterfeit Section said it's rare for criminals to use such sophisticated printing equipment and tools.

"They were looking at creating a bill that was looking closer to the genuine one," Bacon said, referring to the offset printing press seized in the raid. "This is the way of producing a genuine note."

Despite the skills of the criminals behind the bills, Bacon said the forgeries are still far from perfect.

"Notice the water mark on the real bill and the security line. Plus, the real U.S. $100 bank notes change colour in the bottom right hand corner. The fakes miss that," Bacon told CTV's Montreal affiliate, CFCF News.

Although a trained eye could spot the shortcomings with a magnifying glass, he added that "to the general public it would have been a note that could have passed."

Police say the phoney bills -- all U.S. $100 notes produced in the printing shop's off-hours-- have yet to turn up on the streets.

The three suspects were arrested Friday, after a joint investigation by the RCMP and agents of the U.S. Secret Service.

They face possible charges of conspiracy to make counterfeit money as well as possession of counterfeit money.

If convicted, they could face a 14-year prison term.