Thieves have allegedly stolen thousands of pounds after setting up fake bank accounts using their victims’ details.
Police are investigating reports of people having their mail stolen from postboxes in Stanley, Netherton and Agbrigg.
Criminals stole account numbers, addresses and phone numbers from the letters.
The details were then used to set up fake accounts in the victims’ names and loans and credit cards were taken out.
Three people have fallen victim to the scam in Wakefield, as well as another in Leeds.
Two men, aged 37 and 41, from Leeds have been arrested on suspicion of postal theft and have been bailed pending further enquiries.
And police are now appealing for other victims of postal fraud to come forward.
Insp Ian Williams, of the Wakefield neighbourhood police team, said: “Officers are currently conducting enquiries into this alleged scam.
“We have identified potential victims who have had credit cards or even accounts set up in their name of which they have no knowledge.”
In a separate incident thousands of pieces of mail from a Wakefield based mailing box was seized by Trading Standards officers.
West Yorkshire Trading Standards had been alerted when the owner of the business raised concerns that it might be a prize draw scam.
West Yorkshire Trading Standards Service seized more than 4,000 pieces of mail and identified more than 3,600 victims. More than £3,230 was discovered in the envelopes.
The National Scams Team, which was set up to tackle scam mail, is now returning the money to the victims.