Seven suspects and more than 45 people classed as "persons of interest" have been identified by police investigating the Horizon Post Office scandal.
A "scaled-up" national team of officers has been investing for the last six months in Operation Olympos, which specifically looks at Horizon Post Office scandal-related crimes.
The team, consisting of 100 officers nationwide, has found seven suspects since before Christmas.
Four have been interviewed under caution as the investigation continues.
Commander Stephen Clayman, Gold Command for Operation Olympos, has hailed a "huge shift" in the police probe as it has made "significant progress".
He said: "We've got over four million documents that are going to rise to about six million documents.
"But we're beginning to methodically work through those and looking at individuals who are associated with certain prosecutions."
He added there was a "pool of about 45 people plus" labelled "persons of interest" who may have committed on criminal offences on both an individual and corporate level.
Commander Clayman said that number is "expected to grow", with the force looking to build a "robust case" to pass on to the Crown Prosecution Service.
Some have been questioned n the past while others more recently, he said, adding that police are investigating the offences of perverting the course of justice and perjury.
The "wider pool" of persons of interest consists of Post Office investigators, lawyers, and those in management positions across the Fujitsu IT company and the Post Office.
In 2024, Jerry Brown, Postmaster at Hadleigh branch in Suffolk, told LBC he’d rather charges came late than not at all.
“It’s disappointing that it is going to take another two years or so, but I’m far more interested in them being able to make the right decisions for the prosecutions rather than do it without all the evidence there and run the risk of not achieving the right outcome for postmasters.
“I’d much prefer to wait and ensure all the evidence is there in order to bring strong prosecutions.
“Having watched the inquiry and the evidence, I think it’s quite obvious to most people – whether you’re a postmaster or not – that many of the witnesses were holding back and had very selective memories about what happened at the time.“I think we can all draw our own conclusions from that.”
Between 1999 and 2015, more than 900 subpostmasters were wrongfully prosecuted after faulty Horizon accounting software made it look as though money was missing from their accounts.
The scandal is one of the most widespread miscarriages of justice in British legal history.
A portal has been set up where people with information can send details and documents to investigators.
This week, a committee of MPs has said plans to compensate subpostmasters wronged by the Horizon IT scandal are "still moving far too slowly".
The Department of Business and Trade (DBT) needs to "outline what more it will do to ensure every affected postmaster" is aware of their options for redress, according to the public accounts committee.
The Government announced earlier this month that more than £1 billion has been paid out to subpostmasters across the Horizon-related schemes.
However, many subpostmasters are still awaiting compensation.
