Seventeen people have been arrested in a series of raids and six of those arrested have appeared before magistrates in Leeds charged with fraud offences.
According to police, the alleged fraud involves a number of high-value cheques stolen from financial institutions during the past 18 months.
The details on the cheques were altered and the cheques paid into accounts and the cash then withdrawn.
The names of the financial institutions have not been disclosed by police.
During the raids, which followed months of detective work by the police, hundreds of blank cheques were seized, along with computers, printers and other equipment believed to have been used in the alleged fraud.
Detective chief inspector Paul Langan, head of the economic crime unit in West Yorkshire, says in a statement: “Our message to those people is, as this week’s operation demonstrates, we will investigate you, you will be arrested and we will also strip you of any financial benefit you have made from these crimes using the Proceeds of Crime Act.
“It is also worth highlighting that this investigation came about as a result of the financial institutions’ own internal security systems identifying this criminality orchestrated by an organised crime gang.”