The Metropolitan Police is looking at “potential fraud offences” committed in the Horizon IT scandal.
More than 700 Post Office branch managers were accused of wrongdoing after faulty accounting software made it appear money was missing.
The Met said it was investigating possible fraud offences from these cases.
It comes as 50 new potential victims of the scandal have contacted lawyers following an ITV drama about the issue.
Neil Hudgell, a lawyer who acts for claimants, told the BBC that some of those seeking advice were former sub-postmasters who were prosecuted by the Post Office.
The Met Police said the potential offences could have been related to “monies recovered from sub-postmasters as a result of prosecutions or civil actions”.
The force has already been looking into potential offences of perjury and perverting the course of justice in relation to investigations and prosecutions carried out by the Post Office.
Two people have been interviewed under caution but nobody has been arrested since the investigation was launched in January 2020.
Between 1999 and 2015 more than 700 sub-postmasters were accused of wrongdoing based on information from a faulty accounting system, Horizon.
The Metropolitan Police said on Friday evening, as originally reported by the Times, that officers were “investigating potential fraud offences arising out of these prosecutions” which included “monies recovered from sub-postmasters as a result of prosecutions or civil actions”.
The force also said in the statement: “The Met is investigating potential offences of perjury and perverting the course of justice.
“These potential offences arise out of investigations and prosecutions carried out by the Post Office.
“The investigation was launched in January 2020 following a referral from the DPP [Director of Public Prosecutions].
“Two people have been interviewed under caution. Nobody has been arrested.”
Some sub-postmasters wrongfully went to prison, many were financially ruined, forced to declare bankruptcy, while others describe being shunned by their communities following convictions for false accounting and theft. Some have since died.
The case has been described as one of the most widespread miscarriages of justice in British history.
To date, 93 convictions have been overturned and of those, only 27 people have agreed “full and final settlements”.
Some 54 cases have resulted in a conviction being upheld, people being refused permission to appeal or the person appealing withdrawing from the process, according to the Post Office.
There has been widespread sympathy for the victims after the four-part mini-series Mr Bates vs the Post Office: The Real Story aired on ITV this week. It centres on the story of sub-postmaster Alan Bates, played by actor Toby Jones, who drove the campaign to expose the scandal.
It focuses on the legal battle he led and won, paving the way for dozens of convictions to be overturned.
Mr Hudgell, executive chairman of Hudgells, one of the law firms acting for the claimants, says the TV drama has been instrumental in encouraging new cases to come forward.
“The majority of [those 50 new enquiries]… were not prosecuted but lost their livelihoods, lost their homes,” he said.
“But there’s a small handful of people who were convicted that have come forward, three in total at the moment, which is obviously a tiny number proportionate to those that are still out there.”
He also told the BBC that one of the three people that had been convicted has received inpatient psychiatric care.
Mr Hudgell said the drama had brought to light the trauma of what the sub-postmasters went through: “It’s brought huge widespread sympathy to these people so alongside that, family encouragement and speaking to other postmasters that have been along this journey, they have found the courage to come forward.”
Actress Julie Hesmondhalgh, who plays Alan Bates’s partner Suzanne Sercombe in the programme, said she was “completely overwhelmed” by the response to the show and “the outpouring of outrage over the scandal and cover-up”.
“It’s more than any of us dared hope that it would move the campaign along, but sometimes drama can do that. And now: JUSTICE for the thousands affected,” she wrote on X, formerly Twitter.
Several financial compensation schemes have been set up to help those caught up in the scandal, although concerns have been raised about delays in payment.
Prime Minister Rishi Sunak told reporters on Friday: “It’s important that all those affected get the support they need, which I am pleased is happening and we will keep going as quickly as possible.”
Last month, a board overseeing compensation called for all Post Office staff wrongly accused of theft and false accounting to have their convictions overturned.
The Post Office has previously said it encourages “people who believe they were wrongly convicted, for any reason, to consider an appeal”.
